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+publicationDate,title,abstract,id
+2019-05-30,Sub-nanosecond switching in a cryogenic spin-torque spin-valve memory element with a dilute permalloy free layer,"We present a study of the pulsed current switching characteristics of
+spin-valve nanopillars with in-plane magnetized dilute permalloy and undiluted
+permalloy free layers in the ballistic regime at low temperature. The dilute
+permalloy free layer device switches much faster: the characteristic switching
+time for a permalloy free (Ni0.83Fe0.17) layer device is 1.18 ns, while that
+for a dilute permalloy ([Ni0.83Fe0.17]0.6Cu0.4) free layer device is 0.475 ns.
+A ballistic macrospin model can capture the data trends with a reduced spin
+torque asymmetry parameter, reduced spin polarization and increased Gilbert
+damping for the dilute permalloy free layer relative to the permalloy devices.
+Our study demonstrates that reducing the magnetization of the free layer
+increases the switching speed while greatly reducing the switching energy and
+shows a promising route toward even lower power magnetic memory devices
+compatible with superconducting electronics.",1905.13262v1
+2011-12-11,Memory effects in permalloy-niobium hybrid structures,"The kineticts of magnetization reversal of stripe-shaped permalloy-niobium
+hybrid nanofilms is studied in 6-300 K temperature range by means of
+magneto-optics visualization technique. The niobium influence on magnetic
+domain walls type and on magnetic domain structure of permalloy via the
+interface quality and via the distortion of stray fields is found. The memory
+effect, which is the superconducting niobium memory about an initial magnetic
+domain structure of permalloy at cooling below T_c, is found. The memory is
+razed only by hybrid heating over T_c.",1112.2359v1
+2021-01-25,A solution to the permalloy problem,"We propose a solution to the longstanding permalloy problem$-$why the
+particular composition of permalloy, Fe$_{21.5}$Ni$_{78.5}$, achieves a
+dramatic drop in hysteresis, while its material constants show no obvious
+signal of this behavior. We use our recently developed coercivity tool to show
+that a delicate balance between local instabilities and magnetic material
+constants are necessary to explain the dramatic drop of hysteresis at 78.5% Ni.
+Our findings are in agreement with the permalloy experiments and, more broadly,
+provide theoretical guidance for the discovery of novel low hysteresis magnetic
+alloys.",2101.09857v1
+2013-10-29,Influence of sample geometry on inductive damping measurement methods,"We study the precession frequency and effective damping of patterned
+permalloy thin films of different geometry using integrated inductive test
+structures. The test structures consist of coplanar wave guides fabricated onto
+patterned permalloy stripes of different geometry. The width, length and
+position of the permalloy stripe with respect to the center conductor of the
+wave guide are varied. The precession frequency and effective damping of the
+different devices is derived by inductive measurements in time and frequency
+domain in in-plane magnetic fields. While the precession frequencies do not
+reveal a significant dependence on the sample geometry we find a decrease of
+the measured damping with increasing width of the permalloy centered underneath
+the center conductor of the coplanar wave guide. We attribute this effect to an
+additional damping contribution due to inhomogeneous line broadening at the
+edges of the permalloy stripes which does not contribute to the inductive
+signal provided the permalloy stripe is wider than the center conductor.
+Consequences for inductive determination of the effective damping using such
+integrated reference samples are discussed.",1310.7817v1
+2018-05-30,Magnonic band gap and mode hybridization in continuous Permalloy film induced by vertical coupling with an array of Permalloy ellipses,"We investigate magnonic band structure in thin homogeneous permalloy film
+decorated with periodic array of elliptically shaped permalloy dots and
+separated by non-magnetic Pt spacer. We demonstrated experimentally formation
+of the magnonic band structure for Damon-Eshbach wave propagating in permalloy
+film with the band gap opened at the Brillouin zone border and band splitting
+at smaller wavenumbers, due to the Bragg interference and interaction of
+propagating wave of the continuous film with a standing resonant mode of the
+nano-ellipses, respectively. The shape anisotropy of the permalloy nanodots
+allows to control the spin wave dynamics through the switch between two states
+of the magnetization with respect to the underneath film magnetization, thus
+enabling magnonic band structure reprogrammability. With numerical analysis we
+show, that predominant role in formation of the magnonic band structure is
+played by a vertical dynamic coupling between propagating wave in the film and
+magnetization oscillations in the nanodots.",1805.12178v2
+2017-02-17,Magnetic anisotropy in Permalloy: hidden quantum mechanical features,"By means of relativistic, first principles calculations, we investigate the
+microscopic origin of the vanishingly low magnetic anisotropy of Permalloy,
+here proposed to be intrinsically related to the local symmetries of the alloy.
+It is shown that the local magnetic anisotropy of individual atoms in Permalloy
+can be several orders of magnitude larger than that of the bulk sample, and
+5-10 times larger than that of elemental Fe or Ni. We, furthermore, show that
+locally there are several easy axis directions that are favored, depending on
+local composition. The results are discussed in the context of perturbation
+theory, applying the relation between magnetic anisotropy and orbital moment.
+Permalloy keeps its strong ferromagnetic nature due to the exchange energy to
+be larger than the magnetocrystalline anisotropy. Our results shine light on
+the magnetic anisotropy of permalloy and of magnetic materials in general, and
+in addition enhance the understanding of pump-probe measurements and ultrafast
+magnetization dynamics.",1702.05414v1
+2023-11-10,Exchange stiffness proportional to power of magnetization in permalloy co-doped with Mo and Cu,"The exchange stiffness of magnetic materials is one of the essential
+parameters governing magnetic texture and its dynamics in magnetic devices. The
+effect of single-element doping on exchange stiffness has been investigated for
+several doping elements for permalloy (NiFe alloy), a soft magnetic material
+whose soft magnetic properties can be controlled by doping. However, the impact
+of more practical multi-element doping on the exchange stiffness of permalloy
+is unknown. This study investigates the typical magnetic properties, including
+exchange stiffness, of permalloy systematically co-doped with Mo and Cu using
+broadband ferromagnetic resonance spectroscopy. We find that the exchange
+stiffness, which decreases with increasing doping levels, is proportional to a
+power of magnetization, which also decreases with increasing doping levels. The
+magnetization, $M_{\rm s}$, dependence of the exchange stiffness constant, $A$,
+of all the investigated samples, irrespective of the doping levels of each
+element, lies on a single curve expressed as $A\propto M_{\rm s}^n$ with
+exponent $n$ close to 2. This empirical power-law relationship provides a
+guideline for predicting unknown exchange stiffness in non-magnetic
+element-doped permalloy systems.",2311.05852v2
+2004-08-28,"Current-Induced Magnetization Switching in Permalloy-based Nanopillars with Cu, Ag, and Au","We compare magnetoresistances (MR) and switching currents (I_s) at room
+temperature (295K) and 4.2K for Permalloy/N/Permalloy nanopillars undergoing
+current-induced magnetization switching (CIMS), with non-magnetic metals N =
+Cu, Ag, and Au. The N-metal thickness is held fixed at 10 nm. Any systematic
+differences in MR and I_s for the different N-metals are modest, suggesting
+that Ag and Au represent potentially viable alternatives for CIMS studies and
+devices to the more widely used Cu.",0408632v1
+2008-09-01,Quantum transport in ferromagnetic Permalloy nanostructures,"We studied phase coherent phenomena in mesoscopic Permalloy samples by
+exploring low temperature transport. Both, differential conductance as a
+function of bias voltage and magnetoconductance of individual wires display
+conductance fluctuations. Analysis of these fluctuations yields a phase
+coherence length of $\sim250$ nm at 25 mK as well as a $1/\sqrt{T}$ temperature
+dependence. To suppress conductance fluctuations by ensemble averaging we
+investigated low temperature transport in wire arrays and extended Permalloy
+films. In these samples we have measured conductance corrections which stem
+from electron-electron interaction (EEI) but attempts to detect signatures of
+weak localization were without success.",0809.0192v1
+2013-10-15,Transverse spin Seebeck vs. Anomalous and Planar Nernst Effects in Permalloy Thin Films,"Transverse magneto-thermoelectric effects are studied in permalloy thin films
+grown on MgO and GaAs substrates and compared to those grown on suspended SiN
+membranes. The transverse voltage along platinum strips patterned on top of the
+permalloy films is measured vs. the external magnetic field as a function of
+angle and temperature gradient. After the identification of the contribution of
+the planar and anomalous Nernst effects, we find an upper limit for the
+transverse spin Seebeck effect, which is several orders of magnitude smaller
+than previously reported.",1310.4045v1
+2016-12-21,Flexible Bacterial Cellulose Permalloy nanocomposite xerogel sheets size scalable magnetic actuator cum electrical conductor,"Permalloy nanoparticles containing bacterial cellulose hydrogel obtained
+after reduction was compressed into a xerogel flexible sheet by hot pressing at
+60 C at different pressures. The permalloy nanoparticles with an ordered
+structure have a bimodal size distribution centered around 25 nm and 190 nm.
+The smaller nanoparticles are superparamagnetic while the larger particles are
+ferromagnetic at room temperature. The sheets have a room temperature
+magnetisation of 20 emu/g and a coercivity of 32 Oe. The electrical
+conductivity of the flexible sheets increases with hot pressing pressure from 7
+S/cm to 40 S/cm at room temperature.",1701.02792v1
+2019-04-03,Spin diffusion length of Permalloy using spin absorption in lateral spin valves,"We employ the spin absorption technique in lateral spin valves to extract the
+spin diffusion length of Permalloy (Py) as a function of temperature and
+resistivity. A linear dependence of the spin diffusion length with conductivity
+of Py is observed, evidencing that Elliott-Yafet is the dominant spin
+relaxation mechanism in Permalloy. Completing the data set with additional data
+found in literature, we obtain $\lambda_{Py}= (0.91\pm 0.04) (f\Omega
+m^2)/\rho_{Py}$.",1904.01921v1
+2003-07-12,Nanoscale Zeeman localization of charge carriers in diluted magnetic semiconductor-permalloy hybrids,"We investigate the possibility of charge carrier localization in magnetic
+semiconductors due to the presence of a highly inhomogeneous external magnetic
+field. As an example, we study in detail the properties of a magnetic
+semiconductor-permalloy disk hybrid system. We find that the giant Zeeman
+respose of the magnetic semiconductor in conjuction with the highly non-uniform
+magnetic field created by the vortex state of a permalloy disk can lead to
+Zeeman localized states at the interface of the two materials. These trapped
+state are chiral, with chirality controlled by the orientation of the core
+magnetization of the permalloy disk. We calculate the energy spectrum and the
+eigenstates of these Zeeman localized states, and discuss their experimental
+signatures in spectroscopic probes.",0307305v1
+2018-04-17,Reprogrammable magnonic band structure of layered Permalloy/Cu/Permalloy nanowires,"Reprogrammability of magnonic band structure in layered
+Permalloy/Cu/Permalloy nanowires is demonstrated to depend on the relative
+orientation of the two layers magnetization. By using Brillouin light
+spectroscopy, we show that when the layers are aligned parallel two dispersive
+modes, with positive and negative group velocity, are observed while when the
+magnetic layers are aligned anti-parallel, only one dispersive mode, with
+positive group velocity, is detected. Our findings are successfully compared
+and interpreted in terms of a microscopic (Hamiltonian-based) method. An
+explanation for the observed behavior can be attributed to mode-mixing (or
+hybridization) effect when the two magnetic layers are aligned anti-parallel.
+This work opens the path to magnetic field-controlled reconfigurable magnonic
+crystals with multi-modal frequency transmission characteristics.",1804.06217v1
+2019-09-10,Spin Pumping from Permalloy into Uncompensated Antiferromagnetic Co doped Zinc Oxide,"Heterostructures of Co-doped ZnO and Permalloy were investigated for their
+static and dynamic magnetic interaction. The highly Co-doped ZnO is
+paramagentic at room temperature and becomes an uncompensated antiferromagnet
+at low temperatures, showing a narrowly opened hysteresis and a vertical
+exchange bias shift even in the absence of any ferromagnetic layer. At low
+temperatures in combination with Permalloy an exchange bias is found causing a
+horizontal as well as vertical shift of the hysteresis of the heterostructure
+together with an increase in coercive field. Furthermore, an increase in the
+Gilbert damping parameter at room temperature was found by multifrequency FMR
+evidencing spin pumping. Temperature dependent FMR shows a maximum in magnetic
+damping close to the magnetic phase transition. These measurements also
+evidence the exchange bias interaction of Permalloy and long-range ordered
+Co-O-Co structures in ZnO, that are barely detectable by SQUID due to the
+shorter probing times in FMR.",1909.04362v3
+2021-06-21,Resonant Measurement of Non-Reorientable Spin-Orbit Torque from a Ferromagnetic Source Layer Accounting for Dynamic Spin Pumping,"Using a multilayer structure containing (cobalt detector layer)/(copper
+spacer)/(Permalloy source layer), we show experimentally how the
+non-reorientable spin-orbit torque generated by the Permalloy source layer (the
+component of spin-orbit torque that does not change when the Permalloy
+magnetization is rotated) can be measured using spin-torque ferromagnetic
+resonance (ST-FMR) with lineshape analysis. We find that dynamic spin pumping
+between the magnetic layers exerts torques on the magnetic layers as large or
+larger than the spin-orbit torques, so that if dynamic spin pumping is
+neglected the result would be a large overestimate of the spin-orbit torque.
+Nevertheless, the two effects can be separated by performing ST-FMR as a
+function of frequency. We measure a non-reorientable spin torque ratio
+$\xi_{\text{Py}} = 0.04 \pm 0.01$ for spin current flow from Permalloy through
+an 8 nm Cu spacer to the Co, and a strength of dynamic spin pumping that is
+consistent with previous measurements by conventional ferromagnetic resonance.",2106.11127v1
+2014-06-01,Diffusivities and kinetics of short-range and long-range orderings in Ni-Fe permalloys,"The microscopic model of atomic diffusion is considered to describe the
+short-range order relaxation kinetics within the f.c.c.-Ni-Fe Permalloys. The
+model takes into account both the discrete and anisotropic characters of atomic
+jumps within the long-range field of concentration heterogeneities of the
+interacting atoms. The diffusion coefficients and activation energies for the
+disordered Ni-Fe permalloy are estimated with the evaluated probabilities of
+atomic jumps. As shown, the increasing of a temperature with a fixed
+composition influences on the 'potential' field of interatomic interaction
+ambiguously: the field 'potential' increases for defined coordination shells
+and decreases for some of other ones. Although the temperature increasing
+promotes the increasing of any atomic-probabilities jumps generally, but
+decreasing of the action of 'potential' field generated by the atoms of defined
+element and caused by its concentration heterogeneities onto the distant sites
+results in increasing of the atomic-jumps' probabilities of just this element,
+first of all, into the sites, which are more distant from the 'source' of
+heterogeneity. Within the framework of the static concentration waves' method
+along with the self-consistent field approximation, the Onsager-type kinetics
+equation is obtained to describe the long-range order relaxation by the
+L12-type superstructure. To calculate diffusivities for the ordered Ni3Fe
+permalloy, the independent, diffraction experimental data of the long-range
+order parameter relaxation are used. Theoretical curves of the long-range order
+time evolution for the non-stoichiometric f.c.c.-Ni-Fe permalloys are plotted.
+Decreasing of the concentration of alloying element results in decelerating of
+the long-range order parameter change and in increasing of its relaxation time.",1406.0147v1
+2023-03-07,The Role of Self-Torques in Transition Metal Dichalcogenide/Ferromagnet Bilayers,"Recently, transition metal dichalcogenides (TMDs) have been extensively
+studied for their efficient spin-orbit torque generation in TMD/ferromagnetic
+bilayers, owing to their large spin-orbit coupling, variety in crystal
+symmetries, and pristine interfaces. Although the TMD layer was considered
+essential for the generation of the observed SOTs, recent reports show the
+presence of a self-torque in single-layer ferromagnetic devices with magnitudes
+comparable to TMD/ferromagnetic devices. Here, we perform second-harmonic Hall
+SOT measurements on metal-organic chemical vapor deposition (MOCVD) grown
+MoS$_{2}$/permalloy/Al$_{2}$O$_{3}$ devices and compare them to a single-layer
+permalloy/Al$_{2}$O$_{3}$ device to accurately disentangle the role of
+self-torques from contributions from the TMD layer. We report a damping-like
+self-torque conductivity of opposite sign in our single-layer
+permalloy/Al$_{2}$O$_{3}$ device compared to one
+MoS$_{2}$/permalloy/Al$_{2}$O$_{3}$ device, and find no significant one for all
+other MoS$_{2}$/permalloy/Al$_{2}$O$_{3}$ devices. This indicates a competition
+between the self-torque and the torque arising from the TMD layer, which would
+reduce the observed torque in these bilayers. In addition, we find a field-like
+spin-torque conductivity of comparable magnitude to control
+MoS$_{2}$/permalloy/Al$_{2}$O$_{3}$ devices, indicating only a minor role of
+the MoS$_{2}$ layer. Finally, we find a linear dependence of the SOT
+conductivity on the Hall bar leg/channel width ratio of our devices, indicating
+that the Hall bar dimensions are of significant importance for the reported SOT
+strength. Our results accentuate the importance of delicate details, like
+device asymmetry, Hall bar dimensions, and self-torque generation, for the
+correct disentanglement of the microscopic origins underlying the SOTs,
+essential for future energy-efficient spintronic applications.",2303.03892v2
+2003-07-21,Dynamics of ferromagnetic nanomagnets with vortex or single-domain configuration,"We study the dynamics of flat circular permalloy nanomagnets for 1.) magnetic
+vortex and 2.) single-domain configurations, using micromagnetic simulation.
+Dynamical studies for isolated vortex structures show that both the vorticity
+and the central polarity of the out-of-plane component can be switched fast
+(50-100 ps) and independently. Micromagnetic simulations of the switching
+process in thin cylindrical Permalloy (Py) nanoparticles with an initial stable
+single-domain state show nearly homogeneous single-domain behaviour followed by
+excitation of spin waves.",0307503v1
+2003-11-18,Domain-specific magnetization reversals on a permalloy square ring array,"We present domain-specific magnetization reversals extracted from soft x-ray
+resonant magnetic scattering measurement on a permalloy square ring array. The
+extracted domain-specific hysteresis loops reveal that the magnetization of the
+domain parallel to the field is strongly pinned, while those of other domains
+rotate continuously. In comparison with the micromagnetic simulation, the
+hysteresis loop on the pinned domain indicates a possibility of the coexistence
+of the square rings with the vortex and onion states.",0311417v1
+2006-04-05,Anisotropy of Magnetization Reversal and Magnetoresistance in Square Arrays of Permalloy Nano-Rings,"Magnetization reversal mechanisms and impact of magnetization direction are
+studied in square arrays of interconnected circular permalloy nanorings using
+MOKE, local imaging, numerical simulations and transport techniques.",0604132v1
+2007-02-02,Current-induced magnetic vortex core switching in a Permalloy nanodisk,"We report on the switching of a magnetic vortex core in a sub-micron
+Permalloy disk, induced by a short current pulse applied in the film plane.
+Micromagnetic simulations including the adiabatic and non-adiabatic spin-torque
+terms are used to investigate the current-driven magnetization dynamics. We
+predict that a core reversal can be triggered by current bursts a tenth of a
+nanosecond long. The vortex core reversal process is found to be the same as
+when an external field pulse is applied. The control of a vortex core's
+orientation using current pulses introduces the technologically relevant
+possibility to address individual nanomagnets within dense arrays.",0702048v1
+2008-02-06,Self-organized plane arrays of metallic magnetic elements,"We studied the dynamic magnetic properties of plane periodical arrays of
+circular permalloy nano-dots fabricated using a self-organized mask formed by
+polysterene nanospheres on the surface of a Permalloy film. Conventional
+(microwave cavity) and broadband coplanar-line ferromagnetic resonance setups
+were used for the measurements. We found several well resolved resonance peaks.
+This result shows that the self-organized mask fabrication technique is able to
+produce high-quality samples with small dispersion of geometrical and magnetic
+parameters.",0802.0731v1
+2008-07-11,Probing the spin polarization of current by soft X-ray imaging of current-induced magnetic vortex dynamics,"Time-resolved soft X-ray transmission microscopy is applied to image the
+current-induced resonant dynamics of the magnetic vortex core realized in a
+micronsized Permalloy disk. The high spatial resolution better than 25 nm
+enables us to observe the resonant motion of the vortex core. The result also
+provides the spin polarization of the current to be 0.67 +/-0.16 for Permalloy
+by fitting the experimental results with an analytical model in the framework
+of the spin-transfer torque.",0807.1782v1
+2008-11-03,Domain wall propagation in Permalloy nanowires with a thickness gradient,"The domain wall nucleation and motion processes in Permalloy nanowires with a
+thickness gradient along the nanowire axis have been studied. Nanowires with
+widths, w = 250 nm to 3 um and a base thickness of t = 10 nm were fabricated by
+electron-beam lithography. The magnetization hysteresis loops measured on
+individual nanowires are compared to corresponding nanowires without a
+thickness gradient. The Hc vs. t/w curves of wires with and without a thickness
+gradient are discussed and compared to micromagnetic simulations. We find a
+metastability regime at values of w, where a transformation from transverse to
+vortex domain wall type is expected.",0811.0245v2
+2009-05-13,Observation of spin-wave propagation in permalloy microstripes,"We report on the propagation of spin waves in permalloy microstripes. By
+means of scanning Kerr microscopy combined with continuous microwave
+excitation, we detect the time evolution of spin-wave interference patterns in
+an external magnetic field. Assuming transverse spin-wave quantization we can
+directly measure the amplitude, phase velocity and damping for the
+corresponding transversal wave mode numbers m. We find that the spin-wave
+interference pattern is dominated by m=0 and m=2 with phase velocities v_0=71
+km/s and v_2=47 km/s, respectively.",0905.2172v1
+2009-06-12,Six-fold configurational anisotropy and magnetic reversal in nanoscale Permalloy triangles,"Six-fold configurational anisotropy was studied in Permalloy triangles, in
+which the shape symmetry order yields two energetically non-degenerate
+micromagnetic configurations of the spins, the so-called ""Y"" and ""buckle""
+states. A twelve pointed switching astroid was measured using magneto-optical
+experiments and successfully reproduced numerically, with different polar
+quadrants identified as specific magnetic transitions, thereby giving a
+comprehensive view of the magnetic reversal in these structures. A detailed
+analysis highlighted the necessity to include the physical rounding of the
+structures in the simulations to account for the instability of the Y state.",0906.2322v1
+2009-07-14,Localized ferromagnetic resonance force microscopy in permalloy-cobalt films,"We report Ferromagnetic Resonance Force Microscopy (FMRFM) experiments on a
+justaposed continuous films of permalloy and cobalt. Our studies demonstrate
+the capability of FMRFM to perform local spectroscopy of different
+ferromagnetic materials. Theoretical analysis of the uniform resonance mode
+near the edge of the film agrees quantitatively with experimental data. Our
+experiments demonstrate the micron scale lateral resolution in determining
+local magnetic properties in continuous ferromagnetic samples.",0907.2415v1
+2009-09-09,Rapid Domain Wall Motion in Permalloy Nanowires Excited by Spin-Polarized Current Applied Perpendicular to the Nanowire,"We study domain wall (DW) dynamics in permalloy nanowires excited by
+alternating spin-polarized current applied perpendicular to the nanowire. Spin
+torque ferromagnetic resonance measurements reveal that DW oscillations at a
+pinning site in the nanowire can be excited with velocities as high as 800 m/s
+at current densities below 10$^7$ A/cm$^2$.",0909.1822v4
+2009-11-26,Macrospin limit and configurational anisotropy in nanoscale Permalloy triangles,"In Permalloy submicron triangles, configurational anisotropy - a higher-order
+form of shape anisotropy - yields three equivalent easy axes, imposed by the
+structures' symmetry order. Supported by micromagnetic simulations, an
+experimental method was devised to evaluate the nanostructure dimensions for
+which a Stoner-Wohlfarth type of reversal could be used to describe this
+particular magnetic anisotropy. In this regime, a straightforward procedure
+using an in-plane rotating field allowed us to quantify experimentally the
+six-fold anisotropy fields for triangles of different thicknesses and sizes.",0911.5121v1
+2011-03-16,Anomalous-Nernst and anisotropic magnetoresistive heating in a lateral spin valve,"We measured the anomalous-Nernst effect and anisotropic magnetoresistive
+heating in a lateral multiterminal Permalloy/Copper spin valve using
+all-electrical lock-in measurements. To interpret the results, a
+three-dimensional thermoelectric finite-element-model is developed. Using this
+model, we extract the heat profile which we use to determine the anomalous
+Nernst coefficient of Permalloy Rn=0.13 and also determine the maximum angle of
+theta=8 degrees of the magnetization prior to the switching process when an
+opposing non-collinear 10$^{\circ}$ magnetic field is applied.",1103.3305v1
+2011-12-03,Microwave-induced DC Signal in a Permalloy Thin Strip at Low Applied Magnetic Field,"We investigated the ferromagnetic resonance signals in a polycrystalline
+permalloy thin strip under in-plane low static magnetic field. A series of DC
+voltages, which contain ferromagnetic resonance or spin wave resonance signals,
+were measured by inducing microwave frequencies greater than 10 gigahertz. The
+resonant signals measured in low magnetic field show different properties from
+those detected in high field condition. Based on the theory of DC effects in
+ferromagnetic resonance and the experimental data of anisotropic
+magnetoresistance, a quantitative model was proposed. We found that the shape
+anisotropy significantly affects magnetization, and distorts the resonant
+signals in low field condition.",1112.0610v1
+2012-10-30,Microwave assisted resonant domain wall nucleation in permalloy nanowires,"We have designed a system to study microwave assisted domain wall nucleation
+in permalloy nanowires. We find a substantial decrease in the nucleation field
+when microwave fields are applied, in comparison to pulse fields. A clear
+resonance peak is observed in the frequency dependence of the nucleation field,
+which coincides with the uniform mode ferromagnetic resonance frequency. Owing
+to the well-defined nucleation process, the switching field distribution is
+small in contrast to previous reports. Our results show that localized
+microwave field provides an efficient tool for injecting domain walls into
+magnetic nanowires.",1210.7875v1
+2013-03-07,Thickness dependence of the degree of spin polarization of the electrical current in permalloy thin films,"Spin-polarized electrical transport is investigated in $
+Al_{2}O_{3}/Ni_{80}Fe_{20}/Al_{2}O_{3}$ thin films for permalloy thickness
+between 6 and 20nm. The degree of spin-polarization of the current flowing in
+the plane of the film is measured through the current induced spin wave Doppler
+shift. We find that it decreases as the film thickness decreases, from 0.72 at
+20nm to 0.46 at 6nm. This decrease is attributed to a spin depolarization
+induced by the film surfaces. A model is proposed which takes into account the
+contributions of the different sources of electron scattering (alloy disorder,
+phonons, thermal magnons, grain boundaries, film surfaces) to the measured
+spin-dependent resistivities.",1303.1692v1
+2013-08-14,Electrical Detection of Spin Wave Resonance in a Permalloy Thin Strip,"We investigated the microwave-induced DC response of spin wave resonance
+(SWR) in a permalloy thin strip via electrical detection. Our experimental
+results obtained by sweeping the external field reveal that: 1. the amplitude
+of SWR signals depend on the direction of external field and, 2. unlike the DC
+response of ferromagnetic resonance, SWR spectra are always anti-symmetrical.
+The spin dynamics are discussed based on these unusual signals in resonant
+condition.",1308.3069v1
+2014-04-04,Control of domain wall motion at vertically etched nanotrench in ferromagnetic nanowires,"We study field-induced domain wall motion in permalloy nanowires with
+vertically etched nanotrench pinning site. Micromagnetic simulations and
+electrical measurements are employed to characterize the pinning potential at
+the nanotrench. It is found that the potential profile for a transverse wall
+significantly differs from that of a vortex wall, and there is a correlation
+between the pinning strength and the potential profile. Reliable domain wall
+pinning and depinning is experimentally observed from a nanotrench in permalloy
+nanowires. This demonstrates the suitability of the proposed nanotrench pinning
+sites for domain wall device applications.",1404.1138v1
+2015-03-16,Detection of spin waves in permalloy using planar Hall effect,"Rectification of microwave oscillations of magnetization in a permalloy film
+is realized using planar Hall effect. Two different rectified signals are
+obtained: a signal from the linearly excited uniform magnetization precession
+at the frequency of the external pumping and a signal from the pairs of
+contra-propagating short-wavelength spin waves parametrically generated at a
+half of the pumping frequency. The second, most unusual, rectified signal is
+caused by the uniform component of the dynamic magnetization created due to the
+interference of the phase correlated pairs of parametric spin waves.",1503.04638v1
+2017-11-30,Spin glass transition in a thin-film NiO/Permalloy bilayer,"We experimentally study magnetization aging in a thin-film NiO/Permalloy
+bilayer. Aging characteristics are nearly independent of temperature below the
+exchange bias blocking temperature, but rapidly vary above it. The dependence
+on the magnetic history qualitatively changes across this temperature. The
+observed behaviors are consistent with the spin glass transition at the
+exchange bias blocking temperature, with significant implications for magnetism
+and magnetoelectronic phenomena in antiferromagnet/ferromagnet bilayers.",1711.11544v1
+2018-07-27,Thick Permalloy films for the imaging of spin texture dynamics in perpendicularly magnetized systems,"We demonstrated that thick Permalloy films exhibiting a weak growth-induced
+perpendicular magnetic anisotropy can be employed as an ideal test system for
+the investigation of gyration dynamics in topologically trivial and non-trivial
+magnetic states ranging from an isolated magnetic skyrmion to more complex
+n$\pi$ spin configurations.",1807.10654v1
+2021-03-15,Ferromagnetic Resonance in Permalloy Metasurfaces,"Permalloy films with one-dimensional (1D) profile modulation of submicron
+periodicity are fabricated based on commercially available DVD-R discs and
+studied using ferromagnetic resonance (FMR) method and micromagnetic numerical
+simulations. The main resonance position shows in-plane angular dependence
+which is strongly reminiscent of that in ferromagnetic films with uniaxial
+magnetic anisotropy. The main signal and additional low field lines are
+attributed to multiple standing spin wave resonances defined by the grating
+period. The results may present interest in magnetic metamaterials and
+magnonics applications.",2103.08704v1
+2016-03-02,Ferromagnetic resonance in submicron permalloy stripes,"We present the results of systematic experimental investigations and
+micromagnetic simulations for the ferromagnetic resonance in rectangular
+permalloy microstripes. It is shown that the resonant magnetization
+oscillations have a complex spatial structure including a quasi-homogeneous
+precession, lateral spin-wave resonances and localized edge modes, which
+strongly depend on sample orientation in an external magnetic field.",1603.00694v1
+2019-09-05,Magnetically dependent plasmon drag in permalloy structures,"Significant photovoltages are observed in permalloy grating-like structures
+in response to pulsed laser light illumination. Electric signals are enhanced
+at plasmon resonance conditions and show a clear dependence on the magnetic
+field with a characteristic hysteresis. Estimations show that the effect could
+not be explained solely by the laser-induced heating. Alternative mechanisms
+are discussed.",1909.02675v3
+2022-09-22,Barkhausen noise from formation of 360$^{\circ}$ domain walls in disordered permalloy thin films,"Barkhausen noise in disordered ferromagnets is typically understood to
+originate primarily from jerky field-driven motion of domain walls. We study
+the magnetization reversal process in disordered permalloy thin films using
+micromagnetic simulations, and find that the magnetization reversal process
+consists of gradual formation of immobile 360$^{\circ}$ domain walls via a
+sequence of localized magnetization rotation events. The density of
+360$^{\circ}$ domain walls formed within the sample as well as the statistical
+properties of the Barkhausen jumps are controlled by the disorder strength.",2209.10847v2
+2023-03-28,Role of intersublattice exchange interaction on ultrafast longitudinal and transverse magnetization dynamics in Permalloy,"We report about element specific measurements of ultrafast demagnetization
+and magnetization precession damping in Permalloy (Py) thin films.
+Magnetization dynamics induced by optical pump at $1.5$eV is probed
+simultaneously at the $M_{2,3}$ edges of Ni and Fe with High order Harmonics
+for moderate demagnetization rates (less than $50$%). The role of the
+intersublattice exchange interaction on both longitudinal and transverse
+dynamics is analyzed with a Landau Lifshitz Bloch description of
+ferromagnetically coupled Fe and Ni sublattices. It is shown that the
+intersublattice exchange interaction governs the dissipation during
+demagnetization as well as precession damping of the magnetization vector.",2303.15837v1
+2005-04-16,Spin-Transfer Excitations of Permalloy Nanopillars for Large Applied Currents,"Using measurements of the spectra of microwave-frequency resistance
+oscillations, we determine the phase diagram of magnetic excitations caused by
+torques from DC spin-polarized currents in (thin permalloy)/copper/(thick
+permalloy) multilayer samples. We extend the measurements to larger values of
+current than have been reported previously. We find several additional modes
+that we are able to identify with motion of the thick magnetic layer as well as
+the thin one. Peaks in the microwave spectra at multiple frequencies suggest
+that spatially non-uniform dynamical states can be important in some
+circumstances. We compare the experimental phase diagram with simple
+theoretical models and achieve a good qualitative agreement.",0504402v1
+2010-06-29,Magnetic properties of exchange biased and of unbiased oxide/permalloy thin layers: a ferromagnetic resonance and Brillouin scattering study,"Microstrip ferromagnetic resonance and Brillouin scattering are used to
+provide a comparative determination of the magnetic parameters of thin
+permalloy layers interfaced with a non-magnetic (Al2O3) or with an
+antiferromagnetic oxide (NiO). It is shown that the perpendicular anisotropy is
+monitored by an interfacial surface energy term which is practically
+independent of the nature of the interface. In the investigated interval of
+thicknesses (5-25 nm) the saturation magnetisation does not significantly
+differ from the reported one in bulk permalloy. In-plane uniaxial anisotropy
+and exchange-bias anisotropy are also derived from this study of the dynamic
+magnetic excitations and compared to our independent evaluations using
+conventional magnetometry",1006.5598v1
+2013-04-08,Temperature dependence of spin polarization in ferromagnetic metals using lateral spin valves,"A high reproducibility in the performance of cobalt/copper and
+permalloy/copper lateral spin valves with transparent contacts is obtained by
+optimizing the interface quality and the purity of copper. This allows us to
+study comprehensively the spin injection properties of both ferromagnetic
+materials, as well as the spin transport properties of copper, which are not
+affected by the used ferromagnetic material, leading to long spin diffusion
+lengths. Spin polarizations of permalloy and cobalt are obtained as a function
+of temperature. Analysis of the temperature dependence of both the spin
+polarization and conductivity of permalloy using the standard two-channel model
+for ferromagnetic metals suggests that a correction factor of ~2 is needed for
+the spin polarization values obtained by lateral spin valve experiments.",1304.2123v3
+2015-02-28,Large amplitude vortex gyration in Permalloy/Bi$_2$Se$_3$-like heterostructures,"We consider the excitation of large amplitude gyrotropic vortex core
+precession in a Permalloy nanodisk by the torques originating from the in-plane
+microwave current flowing along the interface of the Permalloy/Bi$_2$Se$_3$
+heterostructures, in which the huge charge-to-spin conversion ratio is observed
+\cite{Mellnik-2014}. We consider analytically and by micromagnetic modelling
+the dependence of this excitation on the frequency and magnitude of the
+microwave current. The analogies of the vortex dynamics and the Landau phase
+transitions theory is demonstrated. These findings open the possibility to
+excite gyrotropic vortex motion with the current densities far lower than by
+any other means.",1503.00089v3
+2015-08-21,Radiative damping in wave guide based FMR measured via analysis of perpendicular standing spin waves in sputtered Permalloy films,"The damping $\alpha$ of the spinwave resonances in 75 nm, 120 nm, and 200nm
+-thick Permalloy films is measured via vector-network-analyzer
+ferromagnetic-resonance (VNA-FMR) in the out-of-plane geometry. Inductive
+coupling between the sample and the waveguide leads to an additional radiative
+damping term. The radiative contribution to the over-all damping is determined
+by measuring perpendicular standing spin waves (PSSWs) in the Permalloy films,
+and the results are compared to a simple analytical model. The damping of the
+PSSWs can be fully explained by three contributions to the damping: The
+intrinsic damping, the eddy-current damping, and the radiative damping. No
+other contributions were observed. Furthermore, a method to determine the
+radiative damping in FMR measurements with a single resonance is suggested.",1508.05265v1
+2018-01-22,Spin-orbit torques in NbSe$_2$/Permalloy bilayers,"We present measurements of current-induced spin-orbit torques generated by
+NbSe$_2$, a fully-metallic transition-metal dichalcogenide material, made using
+the spin-torque ferromagnetic resonance (ST-FMR) technique with
+NbSe$_{2}$/Permalloy bilayers. In addition to the out-of-plane Oersted torque
+expected from current flow in the metallic NbSe$_{2}$ layer, we also observe an
+in-plane antidamping torque with torque conductivity $\sigma_{S} \approx 10^{3}
+(\hbar / 2e)$($\Omega$m)$^{-1}$ and indications of a weak field-like
+contribution to the out-of-plane torque oriented opposite to the Oersted
+torque. Furthermore, in some samples we also measure an in-plane field-like
+torque with the form $\hat{m} \times \hat{z}$, where $\hat{m}$ is the Permalloy
+magnetization direction and $\hat{z}$ is perpendicular to the sample plane. The
+size of this component varies strongly between samples and is not correlated
+with the NbSe$_{2}$ thickness. A torque of this form is not allowed by the bulk
+symmetries of NbSe$_{2}$, but is consistent with symmetry breaking by a
+uniaxial strain that might result during device fabrication.",1801.07281v1
+2019-02-10,Spin dynamics of anisotropic azimuthal modes in heterogeneous magnetic nanodisks,"It is well known that azimuthal spin wave modes of magnetic vortex state in
+permalloy nanodisks have circular symmetry. Intuitively, magnetic materials
+having magnetocrystalline anisotropy is not compatible with the circular
+symmetry of the azimuthal modes. In this article, however, we report cubic
+azimuthal modes in heterogeneous nanodisks consisting of a permalloy core and a
+Fe shell. The fourfold symmetry of azimuthal modes is due to the exchange, and
+magneto-static, interactions between the permalloy core and the Fe shell. In
+comparison to results of circular azimuthal mode, the vortex switching occurs
+considerably faster under the excitation of cubic azimuthal mode. The gyration
+path of vortex core turns into square under the influence of induced cubic
+anisotropy in the Py region. We find out periodic oscillation of the vortex
+core size and the gyration speed as well. Our findings may offer a new route
+for spintronic applications using heterogeneous magnetic nanostructures.",1902.03536v1
+2019-02-26,Strong magnon-photon coupling in ferromagnet-superconducting resonator thin-film devices,"We demonstrate strong magnon-photon coupling of a thin-film permalloy device
+fabricated on a coplanar superconducting resonator. A coupling strength of
+0.152 GHz and a cooperativity of 68 are found for a 30-nm-thick permalloy
+stripe. The coupling strength is tunable by rotating the biasing magnetic field
+or changing the volume of permalloy. We also observe an enhancement of
+magnon-photon coupling in the nonlinear regime of the superconducting
+resonator, which is mediated by the nucleation of dynamic flux vortices. Our
+results demonstrate a critical step towards future integrated hybrid systems
+for quantum magnonics and on-chip coherent information transfer.",1902.09715v1
+2019-03-07,Interplay between intra- and inter-nanowires dynamic dipolar interactions in the spin wave band structure of Py/Cu/Py nanowires,"We have studied both experimentally and theoretically the reprogrammable spin
+wave band structure in Permalloy(10nm)/Cu(5nm)/Permalloy(30nm) nanowire arrays
+of width w=280 nm and inter-wire separation in the range from 80 to 280 nm. We
+found that, depending on the inter-wire separation, the anti-parallel
+configuration, where the magnetizations of the two Permalloy layers point in
+opposite directions, is stabilized over specific magnetic field ranges thus
+enabling us to directly compare the band structure with that of the parallel
+alignment. We show that collective spin waves of the Bloch type propagate
+through the arrays with different magnonic bandwidths as a consequence of the
+interplay between the intra- and inter-nanowire dynamic dipolar interactions. A
+detailed understanding, e.g. whether they have a stationary or propagating
+character, is achieved by considering the phase relation (in-phase or
+out-of-phase) between the dynamic magnetizations in the two ferromagnetic
+layers and their average value. This work opens the path to magnetic
+field-controlled reconfigurable layered magnonic crystals that can be used for
+future nanoscale magnon spintronic devices.",1903.02935v1
+2019-09-03,Self-induced inverse spin Hall effect in ferromagnets: demonstration through non-monotonous temperature-dependence in permalloy,"We investigated the self-induced inverse spin Hall effect in ferromagnets.
+Temperature (T), thickness (t) and angular-dependent measurements of transverse
+voltage in spin pumping experiments were performed with permalloy films.
+Results revealed non-monotonous T-dependence of the self-induced transverse
+voltage. Qualitative agreement was found with first-principle calculations
+unravelling the skew scattering, side-jump, and intrinsic contributions to the
+T-dependent spin Hall conductivity. Experimental data were similar whatever the
+material in contact with permalloy (oxides or metals), and revealed an increase
+of produced current with t, demonstrating a bulk origin of the effect.",1909.00976v1
+2022-01-26,Memristive effects in nanopatterned permalloy Kagomé array,"We study memristive effects in Kagom\'{e} nanopatterned permalloy. We observe
+that at low frequencies a thermistor effect is present, a phenomenon arising
+due to the lithography and absent in similar experiments for thin films.
+However, we also show via an independent anisotropic magnetoresistive study
+that a small hysteresis accounting for 1% of the effect is not attributable to
+a thermistive effect. Such effect is also confirmed by a careful subtraction
+scheme between nearby thermal hysteresis. In the millihertz regime, an
+effective model is provided to describe the experimental results for the
+thermistor, showing that there should be a crossover from the millihertz to the
+gigahertz, from a thermistor to an memresistive effect for nanopatterned
+permalloy.",2201.11200v1
+2023-02-04,Tailoring magnetic hysteresis of Fe-Ni permalloy by additive manufacturing: Multiphysics-multiscale simulations of process-property relationships,"Designing the microstructure of Fe-Ni permalloy by additive manufacturing
+(AM) opens new avenues to tailor the materials' magnetic properties. Yet,
+AM-produced parts suffer from spatially inhomogeneous thermal-mechanical and
+magnetic responses, which are less investigated in terms of process simulation
+and modeling schemes. Here we present a powder-resolved multiphysics-multiscale
+simulation scheme for describing magnetic hysteresis in materials produced via
+AM. The underlying physical processes are explicitly considered, including the
+coupled thermal-structural evolution, chemical order-disorder transitions, and
+associated thermo-elasto-plastic behaviors. The residual stress is identified
+as the key thread in connecting the physical processes and in-process phenomena
+across scales. By employing this scheme, we investigate the dependence of the
+fusion zone size, the residual stress and plastic strain, and the magnetic
+hysteresis of AM-produced Fe21.5Ni78.5 permalloy on beam power and scan speed.
+Simulation results also suggest a phenomenological relation between magnetic
+coercivity and average residual stress, which can guide the magnetic hysteresis
+design of soft magnetic materials by choosing appropriate AM-process
+parameters.",2302.02217v1
+2015-09-15,Third type of domain wall in soft magnetic nanostrips,"Magnetic domain walls (DWs) in nanostructures are low-dimensional objects
+that separate regions with uniform magnetisation. Since they can have different
+shapes and widths, DWs are an exciting playground for fundamental research, and
+became in the past years the subject of intense works, mainly focused on
+controlling, manipulating, and moving their internal magnetic configuration. In
+nanostrips with in-plane magnetisation, two DWs have been identified: in thin
+and narrow strips, transverse walls are energetically favored, while in thicker
+and wider strips vortex walls have lower energy. The associated phase diagram
+is now well established and often used to predict the low-energy magnetic
+configuration in a given magnetic nanostructure. However, besides the
+transverse and vortex walls, we find numerically that another type of wall
+exists in permalloy nanostrips. This third type of DW is characterised by a
+three-dimensional, flux closure micromagnetic structure with an unusual length
+and three internal degrees of freedom. Magnetic imaging on
+lithographically-patterned permalloy nanostrips confirms these predictions and
+shows that these DWs can be moved with an external magnetic field of about 1mT.
+An extended phase diagram describing the regions of stability of all known
+types of DWs in permalloy nanostrips is provided.",1509.04762v1
+2016-01-29,Magnetic domain-wall dynamics in wide permalloy strips,"Domain walls in soft permalloy strips may exhibit various equilibrium
+micromagnetic structures depending on the width and thickness of the strip,
+ranging from the well-known transverse and vortex walls in narrow and thin
+strips to double and triple vortex walls recently reported in wider strips [V.
+Est\'evez and L. Laurson, Phys. Rev. B {\bf 91}, 054407 (2015)]. Here we
+analyze the field driven dynamics of such domain walls in permalloy strips of
+widths from 240 nm up to 6 $\mu$m, using the known equilibrium domain wall
+structures as initial configurations. Our micromagnetic simulations show that
+the domain wall dynamics in wide strips is very complex, and depends strongly
+on the geometry of the system, as well as on the magnitude of the driving
+field. We discuss in detail the rich variety of the dynamical behaviors found,
+including dynamic transitions between different domain wall structures,
+periodic dynamics of a vortex core close to the strip edge, transitions towards
+simpler domain wall structures of the multi-vortex domain walls controlled by
+vortex polarity, and the fact that for some combinations of the strip geometry
+and the driving field the system cannot support a compact domain wall.",1601.08060v1
+2017-03-11,Spin-wave dynamics in Permalloy/Cobalt magnonic crystals in the presence of a non-magnetic spacer,"In this paper, we theoretically study the influence of a non-magnetic spacer
+between ferromagnetic dots and ferromagnetic matrix on the frequency dispersion
+of the spin wave excitations in two-dimensional bi-component magnonic crystals.
+By means of the dynamical matrix method we investigate structures inhomogeneous
+across the thickness represented by square arrays of Cobalt or Permalloy dots
+in a Permalloy matrix. We show that the introduction of a non-magnetic spacer
+significantly modifies the total internal magnetic field especially at the
+edges of the grooves and dots. This permits the manipulation of the magnonic
+band structure of spin waves localized either at the edges of the dots or in
+matrix material at the edges of grooves. According to the micromagnetic
+simulations two types of end modes were found. The corresponding frequencies
+are significantly influenced by the end modes localization region. We also show
+that, with the use of a single ferromagnetic material, it is possible to design
+a magnonic crystal preserving properties of bi-component magnonic crystals and
+magnonic antidot lattices. Finally, the influence of the non-magnetic spacers
+on the technologically relevant parameters like group velocity and magnonic
+band width are discussed.",1703.03978v1
+2018-04-11,Thermographic measurements of spin-current-induced temperature modulation in metallic bilayers,"Spin-to-heat current conversion effects have been investigated in bilayer
+films consisting of a paramagnetic metal (PM; Pt, W, or Ta) and a ferromagnetic
+metal (FM; CoFeB or permalloy). When a charge current is applied to the PM/FM
+bilayer film, a spin current is generated across the PM/FM interface owing to
+the spin Hall effect in PM. The spin current was found to exhibit cooling and
+heating features depending on the sign of the spin Hall angle of PM, where the
+spin-current-induced contribution is estimated by subtracting the contribution
+of the anomalous Ettingshausen effect in FM monolayer films. We also found that
+the magnitude of the spin-current-induced temperature modulation in the
+Pt/CoFeB film is greater than but comparable to that in the Pt/permalloy film,
+although the spin dependence of the Peltier coefficient for CoFeB is expected
+to be greater than that for permalloy. We discuss the origin of the observed
+behaviors with the aid of model calculations; the signals in the PM/FM films
+may contain the contributions not only from the electron-driven spin-dependent
+Peltier effect but also from the magnon-driven spin Peltier effect.",1804.04068v1
+2021-05-05,Ni$_{80}$Fe$_{20}$ Nanotubes with Optimized Spintronic Functionalities Prepared by Atomic Layer Deposition,"Permalloy Ni$_{80}$Fe$_{20}$ is one of the key magnetic materials in the
+field of magnonics. Its potential would be further unveiled if it could be
+deposited in three dimensional (3D) architectures of sizes down to the
+nanometer. Atomic Layer Deposition, ALD, is the technique of choice for
+covering arbitrary shapes with homogeneous thin films. Early successes with
+ferromagnetic materials include nickel and cobalt. Still, challenges in
+depositing ferromagnetic alloys reside in the synthesis via decomposing the
+consituent elements at the same temperature and homogeneously. We report
+plasma-enhanced ALD to prepare permalloy Ni$_{80}$Fe$_{20}$ thin films and
+nanotubes using nickelocene and iron(III) tert-butoxide as metal precursors,
+water as the oxidant agent and an in-cycle plasma enhanced reduction step with
+hydrogen. We have optimized the ALD cycle in terms of Ni:Fe atomic ratio and
+functional properties. We obtained a Gilbert damping of 0.013, a resistivity of
+28 $\mu\Omega$cm and an anisotropic magnetoresistance effect of 5.6 $\%$ in the
+planar thin film geometry. We demonstrate that the process also works for
+covering GaAs nanowires, resulting in permalloy nanotubes with high aspect
+ratios and diameters of about 150 nm. Individual nanotubes were investigated in
+terms of crystal phase, composition and spin-dynamic response by microfocused
+Brillouin Light Scattering. Our results enable NiFe-based 3D spintronics and
+magnonic devices in curved and complex topology operated in the GHz frequency
+regime.",2105.01969v1
+2021-06-04,Readout of a antiferromagnetic spintronics systems by strong exchange coupling of Mn2Au and Permalloy,"In antiferromagnetic spintronics, the read-out of the staggered magnetization
+or Neel vector is the key obstacle to harnessing the ultra-fast dynamics and
+stability of antiferromagnets for novel devices. Here, we demonstrate strong
+exchange coupling of Mn2Au, a unique metallic antiferromagnet that exhibits
+Neel spin-orbit torques, with thin ferromagnetic Permalloy layers. This allows
+us to benefit from the well-estabished read-out methods of ferromagnets, while
+the essential advantages of antiferromagnetic spintronics are retained. We show
+one-to-one imprinting of the antiferromagnetic on the ferromagnetic domain
+pattern. Conversely, alignment of the Permalloy magnetization reorients the
+Mn2Au Neel vector, an effect, which can be restricted to large magnetic fields
+by tuning the ferromagnetic layer thickness. To understand the origin of the
+strong coupling, we carry out high resolution electron microscopy imaging and
+we find that our growth yields an interface with a well-defined morphology that
+leads to the strong exchange coupling.",2106.02333v1
+2023-06-26,Control of the asymmetric band structure in Mn2Au by a ferromagnetic driver layer,"Hard X-ray angle-resolved photoemission spectroscopy reveals the
+momentum-resolved band structure in an epitaxial Mn2Au(001) film capped by a 2
+nm thick ferromagnetic Permalloy layer. By magnetizing the Permalloy capping
+layer, the exceptionally strong exchange bias aligns the Neel vector in the
+Mn2Au(001) film accordingly. Uncompensated interface Mn magnetic moments in
+Mn2Au were identified as the origin of the exchange bias using X-ray magnetic
+circular dichroism in combination with photoelectron emission microscopy. Using
+time-of-flight momentum microscopy, we measure the asymmetry of the band
+structure in Mn2Au resulting from the homogeneous orientation of the Neel
+vector. Comparison with theory shows that the Neel vector, determined by the
+magnetic moment of the top Mn layer, is antiparallel to the Permalloy
+magnetization. The experimental results demonstrate that hard X-ray
+photoemission spectroscopy can measure the band structure of epitaxial layers
+beneath a metallic capping layer and corroborate the asymmetric band structure
+in Mn2Au that was previously inferred only indirectly.",2306.14713v1
+2023-11-07,Revealing the ultra-fast domain wall motion in Manganese Gold through permalloy capping,"Antiferromagnets offer much faster dynamics compared to their ferromagnetic
+counterparts but their order parameter is extremely difficult to detect and
+control. So far, controlling the N\'eel order parameter electrically is limited
+to only very few materials where N\'eel spin-orbit torques are allowed by
+symmetry. In this work, we show that coupling a thin ferromagnet (permalloy)
+layer on top of an antiferromagnet (Mn$_2$Au) solves a major roadblock -- the
+controlled reading, writing, and manipulation of antiferromagnetic domains. We
+confirm by atomistic spin dynamics simulations that the domain wall patterns in
+the Mn$_2$Au are imprinted on the permalloy, therefore allowing for indirect
+imaging of the N\'eel order parameter. Our simulations show that the coupled
+domain wall structures in Mn$_2$Au-Py bilayers can be manipulated by either
+acting on the N\'eel order parameter via N\'eel spin-orbit torques or by acting
+on the magnetisation (the ferromagnetic order parameter) via magnetic fields.
+In both cases, we predict ultra-high domain wall speeds on the order of 8.5
+km/s. Thus, employing a thin ferromagnetic layer has the potential to easily
+control the N\'eel order parameter in antiferromagnets even where N\'eel
+spin-orbit torques are forbidden by symmetry. The controlled manipulation of
+the antiferromagnetic order parameter provides a promising basis for the
+development of high-density storage and efficient computing technologies
+working in the THz regime.",2311.04305v1
+2003-05-12,A Novel Broadband Measurement Method for the Magnetoimpedance of Ribbons and Thin Films,"A novel broad-band measurement method of the MI in thin films and ribbons is
+presented. It is based on the automated measurement of the reflection
+coefficient of a cell loaded with the sample. Illustrative results obtained
+with a permalloy multilayer thin film are presented and discussed.",0305259v1
+2004-04-07,Influence of point defects on magnetic vortex structures,"We employed micro-Hall magnetometry and micromagnetic simulations to
+investigate magnetic vortex pinning at single point defects in individual
+submicron-sized permalloy disks. Small ferromagnetic particles containing
+artificial point defects can be fabricated by using an image reversal electron
+beam lithography process. Corresponding micromagnetic calculations, modeling
+the defects within the disks as holes, give reasonable agreement between
+experimental and simulated pinning and depinning field values.",0404159v1
+2007-05-15,Controlled vortex core switching in a magnetic nanodisk by a rotating field,"The switching process of the vortex core in a Permalloy nanodisk affected by
+a rotating magnetic field is studied theoretically. A detailed description of
+magnetization dynamics is obtained by micromagnetic simulations.",0705.2046v2
+2016-07-06,Introduction of spin-orbit interaction into graphene with hydrogenation,"Introduction of spin-orbit interaction (SOI) into graphene with weak
+hydrogenation ($\sim$0.1\%) by dissociation of hydrogen silsesquioxane resist
+has been confirmed through the appearance of inverse spin Hall effect. The spin
+current was produced by spin injection from permalloy electrodes excluding
+non-spin relating experimental artifact.",1607.01558v1
+2023-02-28,Optimization of Permalloy properties for magnetic field sensors using He$^+$ irradiation,"Permalloy, despite being a widely utilized soft magnetic material, still
+calls for optimization in terms of magnetic softness and magnetostriction for
+its use in magnetoresistive sensor applications. Conventional annealing methods
+are often insufficient to locally achieve the desired properties for a narrow
+parameter range. In this study, we report a significant improvement of the
+magnetic softness and magnetostriction in a 30 nm Permalloy film after He$^+$
+irradiation. Compared to the as-deposited state, the irradiation treatment
+reduces the induced anisotropy by a factor ten and the hard axis coercivity by
+a factor five. In addition, the effective magnetostriction of the film is
+significantly reduced by a factor ten - below $1\times10^{-7}$ - after
+irradiation. All the above mentioned effects can be attributed to the isotropic
+crystallite growth of the Ni-Fe alloy and to the intermixing at the magnetic
+layer interfaces under light ion irradiation. We support our findings with
+X-ray diffraction analysis of the textured Ni$_{81}$Fe$_{19}$ alloy.
+Importantly, the sizable magnetoresistance is preserved after the irradiation.
+Our results show that compared to traditional annealing methods, the use of
+He$^+$ irradiation leads to significant improvements in the magnetic softness
+and reduces strain cross sensitivity in Permalloy films required for 3D
+positioning and compass applications. These improvements, in combination with
+the local nature of the irradiation process make our finding valuable for the
+optimization of monolithic integrated sensors, where classic annealing methods
+cannot be applied due to complex interplay within the components in the device.",2302.14455v2
+2000-07-31,Electrical transport properties of bulk Ni$_{c}$Fe$_{1-c}$ alloys and related spin-valve systems,"Within the Kubo-Greenwood formalism we use the fully relativistic,
+spin-polarized, screened Korringa-Kohn-Rostoker method together with the
+coherent-potential approximation for layered systems to calculate the
+resistivity for the permalloy series Ni$_{c}$Fe$_{1-c}$. We are able to
+reproduce the variation of the resistivity across the entire series; notably
+the discontinuous behavior in the vicinity of the structural phase transition
+from bcc to fcc. The absolute values for the resistivity are within a factor of
+two of the experimental data. Also the giant magnetoresistance of a series of
+permalloy-based spin-valve structures is estimated; we are able to reproduce
+the trends and values observed on prototypical spin-valve structures.",0007507v1
+2001-11-06,Spin injection and spin accumulation in permalloy-copper mesoscopic spin valves,"We study the electrical injection and detection of spin currents in a lateral
+spin valve device, using permalloy (Py) as ferromagnetic injecting and
+detecting electrodes and copper (Cu) as non-magnetic metal. Our multi-terminal
+geometry allows us to experimentally distinguish different magneto resistance
+signals, being 1) the spin valve effect, 2) the anomalous magneto resistance
+(AMR) effect and 3) Hall effects. We find that the AMR contribution of the Py
+contacts can be much bigger than the amplitude of the spin valve effect, making
+it impossible to observe the spin valve effect in a 'conventional' measurement
+geometry. However, these 'contact' magneto resistance signals can be used to
+monitor the magnetization reversal process, making it possible to determine the
+magnetic switching fields of the Py contacts of the spin valve device. In a
+'non local' spin valve measurement we are able to completely isolate the spin
+valve signal and observe clear spin accumulation signals at T=4.2 K as well as
+at room temperature. We obtain spin diffusion lengths in copper of 1 micrometer
+and 350 nm at T=4.2 K and room temperature respectively.",0111092v1
+2003-12-18,Optimization of nanostructured permalloy electrodes for a lateral hybrid spin-valve structure,"Ferromagnetic electrodes of a lateral semiconductor-based spin-valve
+structure are designed to provide a maximum of spin-polarized injection
+current. A single-domain state in remanence is a prerequisite obtained by
+nanostructuring Permalloy thin film electrodes. Three regimes of aspect ratios
+$m$ are identified by room temperature magnetic force microscopy: (i)
+high-aspect ratios of $m \ge 20$ provide the favored remanent single-domain
+magnetization states, (ii) medium-aspect ratios $m \sim 3$ to $m \sim 20$ yield
+highly remanent states with closure domains and (iii) low-aspect ratios of $m
+\le 3$ lead to multi-domain structures. Lateral kinks, introduced to bridge the
+gap between micro- and macroscale, disturb the uniform magnetization of
+electrodes with high- and medium-aspect ratios. However, vertical flanks help
+to maintain a uniformly magnetized state at the ferromagnet-semiconcuctor
+contact by domain wall pinning.",0312466v2
+2004-07-21,Detecting domain wall trapping and motion at a constriction in narrow ferromagnetic wires using perpendicular-current giant magnetoresistance,"We present a versatile method for detecting the presence and motion of a
+trapped domain wall in a narrow ferromagnetic layer using
+current-perpendicular-to-plane (CPP) giant magnetoresistance (MR). The CPP-MR
+response to small motions of the trapped domain wall is enhanced because the
+CPP current is restricted to the region of wall trapping. We use a
+Permalloy/Cu/Permalloy spin valve in the shape of a long, ~500-nm-wide wire
+with a constriction (notch) near its middle that acts as a trapping site for a
+head-to-head domain wall. Two different notch shapes were studied, mostly at
+4.2 K but also at 295K.",0407576v1
+2004-12-23,Nanocrystallization and Amorphization Induced by Reactive Nitrogen Sputtering in Iron and Permalloy,"Thin films of iron and permalloy Ni80Fe20 were prepared using an Ar+N2
+mixture with magnetron sputtering technique at ambient temperature. The
+nitrogen partial pressure, during sputtering process was varied in the range of
+0 to 100%, keeping the total gas flow at constant. At lower nitrogen pressures
+RN2<33% both Fe and NiFe, first form a nanocrystalline structure and an
+increase in nitrogen partail pressure results in formation of an amorphous
+structure. At intermediate nitrogen partial pressures, nitrides of Fe and NiFe
+were obtained while at even higher nitrogen partial pressures, nitrides
+themselves became nanocrystalline or amorphous. The surface, structural and
+magnetic properties of the deposited films were studied using x-ray reflection
+and diffraction, transmission electron microscopy, polarized neutron
+reflectivity and using a DC extraction magnetometer. The growth behavior for
+amorphous film was found different as compared with poly or nanocrystalline
+films. The soft-magnetic properties of FeN were improved on nanocrystallization
+while those of NiFeN were degraded. A mechanism inducing nanocrystallization
+and amorphization in Fe and NiFe due to reactive nitrogen sputtering is
+discussed in the present article.",0412657v1
+2005-09-13,Linear magnetic flux amplifier,"By measuring the critical current versus the applied magnetic field
+$I_c(\Phi)$ of an Al superconducting loop enclosing a soft Permalloy magnetic
+dot, we demonstrate that it is feasible to design a linear magnetic flux
+amplifier for applications in superconducting quantum interference devices. The
+selected dimensions of a single-domain Permalloy dot provide that the
+preferential orientation of the magnetization is rotated from the perpendicular
+direction. By increasing an applied magnetic field, the magnetization of the
+dot coherently rotates towards the out-of-plane direction, thus providing a
+flux gain and an enhancement of the sensitivity. As a result of a pronounced
+shape anisotropy, the flux gain generated by the dot can be tuned by adjusting
+the dimensions of the dot.",0509332v1
+2006-06-09,Spin wave dynamics and the determination of intrinsic Gilbert damping in locally-excited Permalloy thin films,"Time-resolved scanning Kerr effect microscopy has been used to study
+magnetization dynamics in Permalloy thin films excited by transient magnetic
+pulses generated by a micrometer-scale transmission line structure. The results
+are consistent with magnetostatic spin wave theory and are supported by
+micromagnetic simulations. Magnetostatic volume and surface spin waves are
+measured for the same specimen using different bias field orientations and can
+be accurately calculated by k-space integrations over all excited plane wave
+components. A single damping constant of Gilbert form is sufficient to describe
+both scenarios. The nonuniform pulsed field plays a key role in the spin wave
+dynamics, with its Fourier transform serving as a weighting function for the
+participating modes. The intrinsic Gilbert damping parameter $\alpha$ is most
+conveniently measured when the spin waves are effectively stationary.",0606235v3
+2006-11-12,Magnetic resonance spectroscopy of perpendicularly magnetized permalloy multilayer disks,"Using a Magnetic Resonance Force Microscope, we compare the ferromagnetic
+resonance spectra of individual micron-size disks with identical diameter, 1
+$m$m, but different layer structures. For a disk composed of a single 43.3 nm
+thick permalloy (Py) layer, the lowest energy mode in the perpendicular
+configuration is the uniform precession. The higher energy modes are standing
+spin-waves confined along the diameter of the disk. For a Cu(30)/Py(100)/Cu(30)
+nm multilayer structure, it has been interpreted that the lowest energy mode
+becomes a precession localized at the Cu/Py interfaces. When the multilayer is
+changed to Py(100)/Cu(10)/Py(10) nm, this localized mode of the thick layer is
+coupled to the precession of the thin layer.",0611307v3
+2007-04-19,Ferromagnetic resonance force microscopy on a thin permalloy film,"Ferromagnetic Resonance Force Microscopy (FMRFM) offers a means of performing
+local ferromagnetic resonance. We have studied the evolution of the FMRFM force
+spectra in a continuous 50 nm thick permalloy film as a function of probe-film
+distance and performed numerical simulations of the intensity of the FMRFM
+probe-film interaction force, accounting for the presence of the localized
+strongly nonuniform magnetic field of the FMRFM probe magnet. Excellent
+agreement between the experimental data and the simulation results provides
+insight into the mechanism of FMR mode excitation in an FMRFM experiment.",0704.2442v1
+2008-02-13,Direct observation of domain wall structures in curved permalloy wires containing an anti-notch,"The formation and field response of head-to-head domain walls in curved
+permalloy wires, fabricated to contain a single anti-notch, have been
+investigated using Lorentz microscopy. High spatial resolution maps of the
+vector induction distribution in domain walls close to the anti-notch have been
+derived and compared with micromagnetic simulations. In wires of 10 nm
+thickness the walls are typically of a modified asymmetric transverse wall
+type. Their response to applied fields tangential to the wire at the anti-notch
+location was studied. The way the wall structure changes depends on whether the
+field moves the wall away from or further into the notch. Higher fields are
+needed and much more distorted wall structures are observed in the latter case,
+indicating that the anti-notch acts as an energy barrier for the domain wall.",0802.1814v1
+2008-12-29,Temperature dependent dynamic and static magnetic response in magnetic tunnel junctions with Permalloy layers,"Ferromagnetic resonance and static magnetic properties of CoFe/Al2O3/CoFe/Py
+and CoFe/Al2O3/CoFeB/Py magnetic tunnel junctions and of 25nm thick
+single-layer Permalloy(Py) films have been studied as a function of temperature
+down to 2K. The temperature dependence of the ferromagnetic resonance excited
+in the Py layers in magnetic tunnel junctions shows knee-like enhancement of
+the resonance frequency accompanied by an anomaly in the magnetization near
+60K. We attribute the anomalous static and dynamic magnetic response at low
+temperatures to interface stress induced magnetic reorientation transition at
+the Py interface which could be influenced by dipolar soft-hard layer coupling
+through the Al2O3 barrier.",0812.4953v1
+2009-03-06,Near-field interaction between domain walls in adjacent Permalloy nanowires,"The magnetostatic interaction between two oppositely charged transverse
+domain walls (DWs)in adjacent Permalloy nanowires is experimentally
+demonstrated. The dependence of the pinning strength on wire separation is
+investigated for distances between 13 and 125 nm, and depinning fields up to 93
+Oe are measured. The results can be described fully by considering the
+interaction between the full complex distribution of magnetic charge within
+rigid, isolated DWs. This suggests the DW internal structure is not appreciably
+disturbed by the pinning potential, and that they remain rigid although the
+pinning strength is significant. This work demonstrates the possibility of
+non-contact DW trapping without DW perturbation and full continuous flexibility
+of the pinning potential type and strength. The consequence of the interaction
+on DW based data storage schemes is evaluated.",0903.1195v1
+2009-11-13,Quantifying spin Hall angles from spin pumping: Experiments and Theory,"Spin Hall effects intermix spin and charge currents even in nonmagnetic
+materials and, therefore, ultimately may allow the use of spin transport
+without the need for ferromagnets. We show how spin Hall effects can be
+quantified by integrating permalloy/normal metal (N) bilayers into a coplanar
+waveguide. A dc spin current in N can be generated by spin pumping in a
+controllable way by ferromagnetic resonance. The transverse dc voltage detected
+along the permalloy/N has contributions from both the anisotropic
+magnetoresistance (AMR) and the spin Hall effect, which can be distinguished by
+their symmetries. We developed a theory that accounts for both. In this way, we
+determine the spin Hall angle quantitatively for Pt, Au and Mo. This approach
+can readily be adapted to any conducting material with even very small spin
+Hall angles.",0911.2725v2
+2010-01-14,Conductance in Co/Al2O3/Si/Al2O3 permalloy with asymmetrically doped barrier,"Permalloy magnetic tunnel junctions. Complementary low frequency noise
+measurements are used to understand the conductance results. The obtained data
+indicate the breakdown of the Coulomb blockade for thickness of the asymmetric
+silicon layer exceeding 1.2\AA . The crossover in the conductance, the
+dependence of the tunnelling magnetoresistance with the bias voltage and the
+noise below 80K correspond to 1 monolayer coverage. Interestingly, the zero
+bias magnetoresistance remains nearly unaffected by the presence of the silicon
+layer. The proposed model uses Larkin-Matveev approximation of tunnelling
+through a single impurity layer generalized to 3D and takes into account the
+variation of the barrier shape with the bias voltage. The main difference is
+the localization of all the impurity levels within a single atomic layer. In
+the high thickness case, up to 1.8\AA, we have introduced a phenomenological
+parameter, which reflects the number of single levels on the total density of
+silicon atoms.",1001.2415v1
+2010-05-04,Effect of disorder studied with ferromagnetic resonance for arrays of tangentially magnetized sub-micron Permalloy discs fabricated by nanosphere lithography,"Tangentially magnetized trigonal arrays of sub-micron Permalloy discs are
+characterized with ferromagnetic resonance to determine the possible
+contributions to frequency and linewidth from array disorder. Each array is
+fabricated by a water-surface self-assembly lithographic technique, and
+consists of a large trigonal array of 700 nm diameter magnetic discs. Each
+array is characterized by a different degree of ordering. Two modes are present
+in the ferromagnetic resonance spectra: a large amplitude, `fundamental' mode
+and a lower amplitude mode at higher field. Angular dependence of the resonance
+field in a very well ordered array is found to be negligible for both modes.
+The relationship between resonance frequency and applied magnetic field is
+found to be uncorrelated with array disorder. Linewidth is found to increase
+with increasing array disorder.",1005.0452v3
+2010-07-06,The dynamics of magnetic vortex states in a single permalloy nanoparticle,"We demonstrate a novel method allowing the study of the magnetic state
+dynamics of a single nanoparticle by means of electron transport measurements.
+Elliptical 550 nm x 240 nm permalloy nanoparticles are wired with non-magnetic
+leads for magnetotransport measurements in the presence of a radio-frequency
+(RF) field. Their resistance exhibits sharp jumps due to the anisotropic
+magnetoresistance even at room temperature. An RF field induces DC voltage
+across the nanoparticle which can be partially depleted at a certain RF
+frequency when a magnetic vortex core resonance is present. An application of
+an additional DC magnetic field eliminates the vortex and reinstates the
+unperturbed DC voltage level. The vortex core resonance frequencies are found
+and the smallest resonance widths are estimated to be less than 6 MHz.",1007.0958v1
+2010-07-19,Standing spin-wave mode structure and linewidth in partially disordered perpendicularly magnetized sub-micron Permalloy disc arrays,"Standing spin wave mode frequencies and linewidths in partially disordered
+perpendicular magnetized arrays of sub-micron Permalloy discs are measured
+using broadband ferromagnetic resonance and compared to analytical results from
+a single, isolated disc. The measured mode structure qualitatively reproduces
+the structure expected from the theory. Fitted demagnetizing parameters
+decrease with increasing array disorder. The frequency difference between the
+first and second radial modes is found to be higher in the measured array
+systems than predicted by theory for an isolated disc. The relative frequencies
+between successive spin wave modes are unaffected by reduction of the
+long-range ordering of discs in the array. An increase in standing spin wave
+resonance linewidth at low applied magnetic fields is observed and grows more
+severe with increased array disorder.",1007.3062v5
+2010-08-16,Domain-wall depinning assisted by pure spin currents,"We study the depinning of domain walls by pure diffusive spin currents in a
+nonlocal spin valve structure based on two ferromagnetic permalloy elements
+with copper as the nonmagnetic spin conduit. The injected spin current is
+absorbed by the second permalloy structure with a domain wall and from the
+dependence of the wall depinning field on the spin current density we find an
+efficiency of 6*10^{-14}T/(A/m^2), which is more than an order of magnitude
+larger than for conventional current induced domain wall motion. Theoretically
+we reproduce this high efficiency, which arises from the surface torques
+exerted by the absorbed spin current that lead to efficient depinning.",1008.2773v1
+2010-09-10,Permalloy-based carbon nanotube spin-valve,"In this Letter we demonstrate that Permalloy (Py), a widely used Ni/Fe alloy,
+forms contacts to carbon nanotubes (CNTs) that meet the requirements for the
+injection and detection of spin-polarized currents in carbon-based spintronic
+devices. We establish the material quality and magnetization properties of Py
+strips in the shape of suitable electrical contacts and find a sharp
+magnetization switching tunable by geometry in the anisotropic
+magnetoresistance (AMR) of a single strip at cryogenic temperatures. In
+addition, we show that Py contacts couple strongly to CNTs, comparable to Pd
+contacts, thereby forming CNT quantum dots at low temperatures. These results
+form the basis for a Py-based CNT spin-valve exhibiting very sharp resistance
+switchings in the tunneling magnetoresistance, which directly correspond to the
+magnetization reversals in the individual contacts observed in AMR experiments.",1009.1960v1
+2010-09-26,Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers,"Spin pumping is a mechanism that generates spin currents from ferromagnetic
+resonance (FMR) over macroscopic interfacial areas, thereby enabling sensitive
+detection of the inverse spin Hall effect that transforms spin into charge
+currents in non-magnetic conductors. Here we study the spin-pumping-induced
+voltages due to the inverse spin Hall effect in permalloy/normal metal bilayers
+integrated into coplanar waveguides for different normal metals and as a
+function of angle of the applied magnetic field direction, as well as microwave
+frequency and power. We find good agreement between experimental data and a
+theoretical model that includes contributions from anisotropic
+magnetoresistance (AMR) and inverse spin Hall effect (ISHE). The analysis
+provides consistent results over a wide range of experimental conditions as
+long as the precise magnetization trajectory is taken into account. The spin
+Hall angles for Pt, Pd, Au and Mo were determined with high precision to be
+$0.013\pm0.002$, $0.0064\pm0.001$, $0.0035\pm0.0003$ and $-0.0005\pm0.0001$,
+respectively.",1009.5089v1
+2010-11-01,Quantitative magnetic force microscopy on permalloy dots using an iron filled carbon nanotube probe,"We have characterized a new Magnetic Force Microscopy (MFM) probe based on an
+iron filled carbon nanotube (FeCNT) using MFM imaging on permalloy (Py) disks
+saturated in a high magnetic field perpendicular to the disk plane. The
+experimental data are accurately modeled by describing the FeCNT probe as
+having a single magnetic monopole at its tip whose effective magnetic charge is
+determined by the diameter of the iron wire enclosed in the carbon nanotube and
+its saturation magnetization 4 \pi M_s ~ 2.2 x 10^4 G. A magnetic monopole
+probe enables quantitative measurements of the magnetic field gradient close to
+the sample surface. The lateral resolution is defined by the diameter of the
+iron wire ~15 nm and the probe-sample separation. As a demonstration, the
+magnetic field gradients close to the surface of a Py dot in domain and vortex
+states were imaged.",1011.0389v1
+2011-03-02,Classification of super domains and super domain walls in permalloy antidot lattices,"We study the remanent domain configurations of rectangular permalloy antidot
+lattices over a range of lattice parameters. The influence of antidot diameter,
+antidot spacing, and the aspect ratio of the lattice on the remanent domain
+configuration are investigated by magnetic force microscopy and supported by
+micromagnetic simulations. In the remanent state, areas of cells with the same
+orientation of average magnetization form magnetic super domains separated by
+super domain walls (SDWs). Two types of SDWs are identified. The first type is
+characterized by low stray field energy, is linear, and expands over many
+lattice constants. In contrast the second type shows high stray field energy
+and is situated at kinks of low energy SDWs. Its width can vary from a minimum
+of two lattice cells up to several lattice constants, depending on the lattice
+parameters. The occurrence and structure of these two types of SDWs as function
+of lattice parameters are classified and discussed in terms of the interplay of
+stray field and exchange energy.",1103.0395v2
+2011-11-26,Quantum depinning of the magnetic vortex core in micron-size permalloy disks,"The vortex state, characterized by an in-plane closed flux domain structure
+and an out-of-plane magnetization at its centre (the vortex core), is one of
+the magnetic equilibria of thin soft ferromagnetic micron-size dots. In the
+last two decades many groups have been working on the dynamics of the magnetic
+moment in nanomagnetic materials at low temperatures, it giving rise to the
+observation of quantum relaxations and quantum hysteresis cycles. For the first
+time, we report experimental evidence of quantum dynamics of the vortex core of
+micron-size permalloy (Fe$_{19}$Ni$_{81}$) disks induced by the application of
+an in-plane magnetic field. It is attributed to the quantum tunneling of the
+vortex core through pinning barriers, which are associated to structural
+defects in the dots, towards its equilibrium position.",1111.6171v1
+2012-06-08,Spin-dependent Seebeck coefficients of Ni_{80}Fe_{20} and Co in nanopillar spin valves,"We have experimentally determined the spin-dependent Seebeck coefficient of
+permalloy (Ni_{80}Fe_{20}) and cobalt (Co) using nanopillar spin valve devices.
+The devices were specifically designed to completely separate heat related
+effects from charge related effects. A pure heat current through the nanopillar
+spin valve, a stack of two ferromagnetic layers (F) separated by a non-magnetic
+layer (N), leads to a thermovoltage proportional to the spin-dependent Seebeck
+coefficient S_{S}=S_{\uparrow}-S_{\downarrow} of the ferromagnet, where
+S_{\uparrow} and S_{\downarrow} are the Seebeck coefficient for spin-up and
+spin-down electrons. By using a three-dimensional finite-element model (3D-FEM)
+based on spin-dependent thermoelectric theory, whose input material parameters
+were measured in separate devices, we were able to accurately determine a
+spin-dependent Seebeck coefficient of -1.8 microvolt/Kelvin and -4.5
+microvolt/Kelvin for cobalt and permalloy, respectively corresponding to a
+Seebeck coefficient polarization P_{S}=S_{S}/S_{F} of 0.08 and 0.25, where
+S_{F} is the Seebeck coefficient of the ferromagnet. The results are in
+agreement with earlier theoretical work in Co/Cu multilayers and spin-dependent
+Seebeck and spin-dependent Peltier measurements in Ni_{80}Fe_{20}/Cu spin valve
+structures.",1206.1659v1
+2012-10-09,Spectral Characteristics of the Microwave Emission by the Spin Hall Nano-Oscillator,"We utilized microwave spectroscopy to study the magnetization oscillations
+locally induced in a Permalloy film by a pure spin current, which is generated
+due to the spin Hall effect in an adjacent Pt layer. The oscillation frequency
+is lower than the ferromagnetic resonance of Permalloy, indicating that the
+oscillation forms a self-localized nonpropagating spin-wave soliton. At
+cryogenic temperatures, the spectral characteristics are remarkably similar to
+the traditional spin-torque nano-oscillators driven by spin-polarized currents.
+However, the linewidth of the oscillation increases exponentially with
+temperature and an additional peak appears in the spectrum below the
+ferromagnetic resonance, suggesting that the spectral characteristics are
+determined by interplay between two localized dynamical states.",1210.2758v2
+2013-09-26,Proximity effect of spin orbit coupling in Pt/Co2FeAl and Pt/Permalloy bilayers_810571,"Proximity effect of spin orbit coupling is investigated through anomalous
+Hall effect in Pt/Co2FeAl and Pt/Permalloy bilayers. A series of nontrivial
+magnetotransport behaviors, resulting from a strong impact of phonons on skew
+scattering, is observed in these films with ultrathin ferromagnetic layers. The
+parameters representing skew scattering, side jump and intrinsic contributions
+are dramatically enhanced when the ferromagnetic layer is very thin, and they
+have clear linear dependences on the reciprocal of ferromagnetic layer
+thickness, indicating a powerful influence of Pt/Ferromagnet interface. Further
+study on Cu/Co2FeAl and Ta/Co2FeAl bilayers reveals that a simple interface
+scattering without intense spin orbit coupling is not sufficient to trigger
+such a phenomenon. The proximity effect of spin orbit coupling is thus
+suggested to occur at the Pt/Ferromagnet interface, and as a result quite large
+anomalous Hall angle (0.036) and Nernst angle (0.23) are confirmed in the
+Pt/CFA films at room temperature.",1309.7023v1
+2014-07-14,Circular single domains in hemispherical small size Permalloy clusters,"We have studied ferromagnetic Permalloy clusters obtained by
+electrodeposition on n-type silicon. Magnetization measurements reveal
+hysteresis loops almost independent on temperature and very similar in shape to
+those obtained in nanodisks with diameter bigger than 150nm. The spin
+configuration for the ground state, obtained by micromagnetic simulation, shows
+topological vortices with random chirality and polarization. This behaviour in
+the small diameter clusters (~80nm), is attributed to the Dzyaloshinskii-Moriya
+interaction that arises in its hemispherical geometries. This magnetization
+behaviour can be utilized to explain the magnetoresistance measured with
+magnetic field in plane and out of sample plane.",1407.3813v2
+2014-07-29,Controllable Schottky Barriers between MoS2 and Permalloy,"MoS2 is a layered two-dimensional material with strong spin-orbit coupling
+and long spin lifetime, which is promising for electronic and spintronic
+applications. However, because of its large band gap and small electron
+affinity, a considerable Schottky barrier exists between MoS2 and contact
+metal, hindering the further study of spin transport and spin injection in
+MoS2. Although substantial progress has been made in improving device
+performance, the existence of metal-semiconductor Schottky barrier has not yet
+been fully understood. Here, we investigate permalloy (Py) contacts to both
+multilayer and monolayer MoS2. Ohmic contact is developed between multilayer
+MoS2 and Py electrodes with a negative Schottky barrier, which yields a high
+field-effect mobility exceeding 55 cm2V-1s-1 at low temperature. Further, by
+applying back gate voltage and inserting different thickness of Al2O3 layer
+between the metal and monolayer MoS2, we have achieved a good tunability of the
+Schottky barrier height (down to zero). These results are important in
+improving the performance of MoS2 transistor devices; and it may pave the way
+to realize spin transport and spin injection in MoS2.",1407.7652v2
+2014-09-22,Magnetic vortex chirality switching in Permalloy nanowires with asymmetric notches,"We have investigated the motion of vortex domain walls passing across non
+symmetric triangular notches in single Permalloy nanowires. We have measured
+hysteresis cycles using the focused magneto-optical Kerr effect before and
+beyond the notch, which allowed to probe beyond the notch the occurrence
+probability of clockwise (CW) and counter-clockwise (CCW) walls in tail-to-tail
+(TT) and head-to-head (HH) configurations. We present experimental evidence of
+chirality flipping provided by the vortex -- notch interaction. With a low exit
+angle the probability of chirality flipping increases and here with the lowest
+angle of 15$^o$ the probability of propagation of the energetically favored
+domain wall configuration (CCW for TT or CW for HH walls) is $\approx 75\%$.
+Micromagnetic simulations reveal details of the chirality reversal dynamics.",1409.6370v2
+2014-10-02,Spin wave non-reciprocity and beating in permalloy by time-resolved magneto-optical Kerr effect,"We have studied the propagation characteristics of spin wave modes in a
+permalloy stripe by time-resolved magneto-optical Kerr effect techniques. We
+observe a beating interference pattern in the time domain under the influence
+of an electrical square pulse excitation at the center of the stripe. We also
+probe the non-reciprocal behavior of propagating spin waves with a dependence
+on the external magnetic field. Spatial dependence studies show that localized
+edge mode spin waves have a lower frequency than spin waves in the center of
+the stripe, due to the varying magnetization vector across the width of the
+stripe.",1410.0441v1
+2014-10-02,Strong coupling between a permalloy ferromagnetic contact and a helical edge channel in a narrow HgTe quantum well,"We experimentally investigate spin-polarized electron transport between a
+permalloy ferromagnet and the edge of a two-dimensional electron system with
+band inversion, realized in a narrow, 8~nm wide HgTe quantum well. In zero
+magnetic field, we observe strong asymmetry of the edge potential distribution
+with respect to the ferromagnetic ground lead. This result indicates, that the
+helical edge channel, specific for the structures with band inversion even at
+the conductive bulk, is strongly coupled to the ferromagnetic side contact,
+possibly due to the effects of proximity magnetization. It allows selective and
+spin-sensitive contacting of helical edge states.",1410.0585v5
+2014-10-30,Intrinsic synchronization of an array of spin-torque oscillators driven by the spin-Hall effect,"This paper micromagnetically studies the magnetization dynamics driven by the
+spin-Hall effect in a Platinum/Permalloy bi-layer. For a certain field and
+current range, the excitation of a uniform mode, characterized by a power with
+a spatial distribution in the whole ferromagnetic cross section, is observed.
+We suggest to use the ferromagnet of the bi-layer as basis for the realization
+of an array of spin-torque oscillators (STOs): the Permalloy ferromagnet will
+act as shared free layer, whereas the spacers and the polarizers are built on
+top of it. Following this strategy, the frequency of the uniform mode will be
+the same for the whole device, creating an intrinsic synchronization. The
+synchronization of an array of parallely connected STOs will allow to increase
+the output power, as necessary for technological applications.",1410.8342v1
+2014-12-29,Domain wall magneto-Seebeck effect,"The interplay between charge, spin, and heat currents in magnetic nano
+systems subjected to a temperature gradient has lead to a variety of novel
+effects and promising applications studied in the fast-growing field of
+spincaloritronics. Here we explore the magnetothermoelectrical properties of an
+individual magnetic domain wall in a permalloy nanowire. In thermal gradients
+of the order of few Kelvin per micrometer along the long wire axis, we find a
+clear magneto-Seebeck signature due to the presence of a single domain wall.
+The observed domain wall magneto-Seebeck effect can be explained by the
+magnetization-dependent Seebeck coefficient of permalloy in combination with
+the local spin configuration of the domain wall.",1412.8289v1
+2015-01-07,Engineering magnetic domain-wall structure in permalloy nanowires,"Using Lorentz transmission electron microscopy we investigate the behavior of
+domain walls pinned at non-topographic defects in Cr(3 nm)/Permalloy(10
+nm)/Cr(5 nm) nanowires of width 500 nm. The pinning sites consist of linear
+defects where magnetic properties are modified by a Ga ion probe with diameter
+~ 10 nm using a focused ion beam microscope. We study the detailed change of
+the modified region (which is on the scale of the focused ion spot) using
+electron energy loss spectroscopy and differential phase contrast imaging on an
+aberration (Cs) corrected scanning transmission electron microscope. The signal
+variation observed indicates that the region modified by the irradiation
+corresponds to ~ 40-50 nm despite the ion probe size of only 10 nm. Employing
+the Fresnel mode of Lorentz transmission electron microscopy, we show that it
+is possible to control the domain wall structure and its depinning strength not
+only via the irradiation dose but also the line orientation.",1501.01410v1
+2015-01-30,Head-to-Head Domain Wall Structures in Wide Permalloy Strips,"We analyze the equilibrium micromagnetic domain wall structures encountered
+in Permalloy strips of a wide range of thicknesses and widths, with strip
+widths up to several micrometers. By performing an extensive set of
+micromagnetic simulations, we show that the equilibrium phase diagram of the
+domain wall structures exhibits in addition to the previously found structures
+(symmetric and asymmetric transverse walls, vortex wall) also double vortex and
+triple vortex domain walls for large enough strip widths and thicknesses. Also
+several metastable domain wall structures are found for wide and/or thick
+strips. We discuss the details of the relaxation process from random
+magnetization initial states towards the stable domain wall structure, and show
+that our results are robust with respect to changes of e.g. the magnitude of
+the Gilbert damping constant and details of the initial conditions.",1501.07731v1
+2015-05-05,Three-dimensional Character of the Magnetization Dynamics in Magnetic Vortex Structures - Hybridization of Flexure Gyromodes with Spin Waves,"Three-dimensional linear spin-wave eigenmodes of a Permalloy disk having
+finite thickness are studied by micromagnetic simulations based on the
+Landau-Lifshitz-Gilbert equation. The eigenmodes found in the simulations are
+interpreted as linear superpositions (hybridizations) of 'approximate'
+three-dimensional eigenmodes, which are the fundamental gyromode $G_0$, the
+spin-wave modes and the higher-order gyromodes $G_N$ (flexure modes), the
+thickness dependence of which is represented by perpendicular standing spin
+waves. This hybridization leads to new and surprising dependencies of the mode
+frequencies on the disk thickness. The three-dimensional character of the
+eigenmodes is essential to explain the recent experimental results on
+vortex-core reversal observed in relatively thick Permalloy disks.",1505.01148v2
+2015-10-23,Mapping the domain wall pinning landscape in ferromagnetic films,"The propagation of domain walls in a ferromagnetic film is largely determined
+by domain wall pinning at defects in the material. In this letter we map the
+effective potential landscape for domain wall pinning in Permalloy films by
+raster scanning a single ferromagnetic vortex and monitoring the hysteretic
+vortex displacement vs. applied magnetic field. The measurement is carried out
+using a differential magneto-optical microscopy technique which yields spatial
+sensitivity $\sim 10$ nm. We present a simple algorithm for extracting an
+effective pinning potential from the measurement of vortex displacement vs.
+applied field. The resulting maps of the pinning potential reveal distinct
+types of pinning sites, which we attribute to quasi-zero-, one-, and
+two-dimensional defects in the Permalloy film.",1510.07059v2
+2015-11-30,Frequency non-reciprocity of surface spin wave in Permalloy thin films,"Surface spin waves in thin Permalloy films are studied by means of
+propagative spin wave spectroscopy. We observe a systematic difference of up to
+several tens of MHz when comparing the frequencies of counter-propagating
+waves. This frequency non-reciprocity effect is modeled using an analytical
+dipole-exchange theory that considers the mutual influence of non-reciprocal
+spin wave modal profiles and differences in magnetic anisotropies at the two
+film surfaces. At moderate film thickness (20 nm and below), the frequency
+non-reciprocity scales linearly with the wave vector and quadratically with the
+thickness, whereas a more complex non-monotonic behavior is observed at larger
+thickness. Our work suggests that surface wave frequency non-reciprocity can be
+used as an accurate spectroscopic probe of magnetic asymmetries in thin
+ferromagnetic films.",1511.09351v1
+2015-12-04,Current and field stimulated motion of domain wall in narrow permalloy stripe,"Of the new types of cryoelectronic devices under development, including phase
+shifters, giant magnetoresistance switches, diodes, transistors, and memory
+cells, some are based on hybrid superconductor-normal metal or
+superconductor-ferromagnet films. Control of these devices is realized by means
+of pulses of voltage, light, or magnetic field. Spin-polarized current may be
+used to switch low-temperature devices, as in spin-electronic devices. In the
+superconducting layer, the current is dissipation less, which would bring large
+reduction of energy consumption. We demonstrate that mag-netic domain walls in
+bilayer niobium-permalloy stripes are shifted by electrical current along the
+stripe even at low tem-perature, with the niobium in the superconducting state.
+The wall motion in response to current pulses is quite different from that
+induced by a magnetic field pulses only. The effect could be used to create a
+new type of sequentially switched serial devices because of very high value of
+the wall velocity, which excides by many orders of magnitude the velocity of
+the wall moved with magnetic field pulses.",1512.01372v1
+2016-02-23,Experimental Investigation of Temperature-Dependent Gilbert Damping in Permalloy Thin Films,"The Gilbert damping of ferromagnetic materials is arguably the most important
+but least understood phenomenological parameter that dictates real-time
+magnetization dynamics. Understanding the physical origin of the Gilbert
+damping is highly relevant to developing future fast switching spintronics
+devices such as magnetic sensors and magnetic random access memory. Here, we
+report an experimental study of temperature-dependent Gilbert damping in
+permalloy (Py) thin films of varying thicknesses by ferromagnetic resonance.
+From the thickness dependence, two independent contributions to the Gilbert
+damping are identified, namely bulk damping and surface damping. Of particular
+interest, bulk damping decreases monotonically as the temperature decreases,
+while surface damping shows an enhancement peak at the temperature of ~50 K.
+These results provide an important insight to the physical origin of the
+Gilbert damping in ultrathin magnetic films.",1602.07325v1
+2016-05-19,Magnetic Domain Wall Engineering in a Nanoscale Permalloy Junction,"Nanoscale magnetic junction provides a useful approach to act as the building
+block for magnetoresistive random access memories (MRAM), where one of the key
+issues is to control the magnetic domain configuration. Here, we study the
+domain structure and the magnetic switching in the Permalloy (Fe20Ni80)
+nanoscale magnetic junctions with different thicknesses by using micromagnetic
+simulations. It is found that both the 90-degree and 45-degree domain walls can
+be formed between the junctions and the wire arms depending on the thickness of
+the device. The magnetic switching fields show distinct thickness dependencies
+with a broad peak varying from 7 nm to 22 nm depending on the junction sizes,
+and the large magnetic switching fields favor the stability of the MRAM
+operation.",1605.05998v2
+2016-08-04,Emergence of the stripe-domain phase in patterned Permalloy films,"The occurrence of stripe domains in ferromagnetic Permalloy
+(Py=Fe$_{20}$Ni$_{80}$) is a well known phenomenon which has been extensively
+observed and characterized. This peculiar magnetic configuration appears only
+in films with a thickness above a critical value ($d_{cr}$), which is strongly
+determined by the sputtering conditions (i.e. deposition rate, temperature,
+magnetic field). So far, $d_{cr}$ has usually been presented as the boundary
+between the homogeneous (H) and stripe-domains (SD) regime, respectively below
+and above $d_{cr}$. In this work we study the transition from the H to the SD
+regime in thin films and microstructured bridges of Py with different
+thicknesses. We find there is an intermediate regime, over a quite significant
+thickness range below d$_{cr}$, which is signaled in confined structures by a
+quickly changing domain-wall configuration and by a broadening of the
+magnetoresistance dip at the coercive field. We call this the emerging
+stripe-domains (ESD) regime. The transition from the ESD to the SD regime is
+accompanied by a sharp increase of the magnetoresistance ratio at the thickness
+where stripes appear in MFM.",1608.01527v1
+2016-09-05,Coarsening dynamics of topological defects in thin Permalloy films,"We study the dynamics of topological defects in the magnetic texture of
+rectangular Permalloy thin film elements during relaxation from random
+magnetization initial states. Our full micromagnetic simulations reveal complex
+defect dynamics during relaxation towards the stable Landau closure domain
+pattern, manifested as temporal power-law decay, with a system-size dependent
+cut-off time, of various quantities. These include the energy density of the
+system, and the number densities of the different kinds of topological defects
+present in the system. The related power-law exponents assume non-trivial
+values, and are found to be different for the different defect types. The
+exponents are robust against a moderate increase in the Gilbert damping
+constant and introduction of quenched structural disorder. We discuss details
+of the processes allowed by conservation of the winding number of the defects,
+underlying their complex coarsening dynamics.",1609.01094v1
+2017-01-20,Fast vortex wall motion in wide Permalloy strips from double switching of the vortex core,"We study vortex domain wall dynamics in wide Permalloy strips driven by
+applied magnetic fields and spin-polarized electric currents. As recently
+reported [V. Est\'evez and L. Laurson, Phys. Rev. B, 93, 064403 (2016)], for
+sufficiently wide strips and above a threshold field, periodic dynamics of the
+vortex core are localized in the vicinity of one of the strip edges, and the
+velocity drop typically observed for narrow strips is replaced by a
+high-velocity plateau. Here, we analyze this behavior in more detail by means
+of micromagnetic simulations. We show that the high-velocity plateau originates
+from a repeated double switching of the magnetic vortex core, underlying the
+periodic vortex core dynamics in the vicinity of the strip edge, i.e., the
+""attraction-repulsion"" effect. We also discuss the corresponding dynamics
+driven by spin-polarized currents, as well as the effect of including quenched
+random structural disorder to the system.",1701.05732v2
+2017-08-05,Spin Injection and Detection via the Anomalous Spin Hall Effect in a Ferromagnetic Metal,"We report a novel spin injection and detection mechanism via the anomalous
+Hall effect in a ferromagnetic metal. The anomalous spin Hall effect (ASHE)
+refers to the transverse spin current generated within the ferromagnet. We
+utilize the ASHE and its reciprocal effect to electrically inject and detect
+magnons in a magnetic insulator in a non-local geometry. Our experiments reveal
+that permalloy can have a higher spin injection and detection efficiency to
+that of platinum, owing to the ASHE. We also demonstrate the tunability of the
+ASHE via the orientation of the permalloy magnetization, thus creating new
+possibilities for spintronic applications.",1708.01752v1
+2017-12-11,Quantitative magneto-optical investigation of superconductor/ferromagnet hybrid structures,"We present a detailed quantitative magneto-optical imaging study of several
+superconductor/ferromagnet hybrid structures, including Nb deposited on top of
+thermomagnetically patterned NdFeB, and permalloy/niobium with erasable and
+tailored magnetic landscapes imprinted in the permalloy layer. The
+magneto-optical imaging data is complemented with and compared to scanning Hall
+probe microscopy measurements. Comprehensive protocols have been developed for
+calibrating, testing, and converting Faraday rotation data to magnetic field
+maps. Applied to the acquired data, they reveal the comparatively weaker
+magnetic response of the superconductor from the background of larger fields
+and field gradients generated by the magnetic layer.",1712.03723v2
+2018-05-29,Efficient injection and detection of out-of-plane spins via the anomalous spin Hall effect in permalloy nanowires,"We report a novel mechanism for the electrical injection and detection of
+out-of-plane spin accumulation via the anomalous spin Hall effect (ASHE), where
+the direction of the spin accumulation can be controlled by manipulating the
+magnetization of the ferromagnet. This mechanism is distinct from the spin Hall
+effect (SHE), where the spin accumulation is created along a fixed direction
+parallel to an interface. We demonstrate this unique property of the ASHE in
+nanowires made of permalloy (Py), to inject and detect out-of-plane spin
+accumulation in a magnetic insulator, yttrium iron garnet (YIG). We show that
+the efficiency for the injection/detection of out-of-plane spins can be up to
+50% of that of in-plane spins. We further report the possibility to detect spin
+currents parallel to the Py/YIG interface for spins fully oriented in the
+out-of-plane direction, resulting in a sign reversal of the non-local magnon
+spin signal. The new mechanisms that we have demonstrated are highly relevant
+for spin torque devices and applications.",1805.11575v1
+2018-11-25,Temperature-Dependent Magnetization Reversal in Exchange Bias NiFe/IrMn/NiFe Structures,"We demonstrate the magnetization reversal features in NiFe/IrMn/NiFe
+thin-film structures with 40% and 75% relative content of Ni in Permalloy in
+the temperature range from 80 K to 300 K. At the descending branches of the
+hysteresis loops, the magnetization reversal sequence of the two ferromagnetic
+layers is found to depend on the type of NiFe alloy. In the samples with 75%
+relative content of Ni, the bottom ferromagnetic layer reverses prior to the
+top one. On the contrary, in the samples with 40% of Ni, the top ferromagnetic
+layer reverses prior to the bottom one. These tendencies of magnetization
+reversal are preserved in the entire range of temperatures. These distinctions
+can be explained by the morphological and structural differences of interfaces
+in the samples based on two types of Permalloy.",1811.09963v1
+2019-11-19,Imaging non-standing spin-waves in confined micron-sized ferromagnetic structures under uniform excitation,"A non-standing character of directly imaged spin-waves in confined
+micron-sized ultrathin permalloy (Ni\textsubscript{80}Fe\textsubscript{20})
+structures is reported along with evidence of the possibility to alter the
+observed state by modifications to the sample geometry. Using micromagnetic
+simulations the presence of the spin-wave modes excited in the permalloy
+stripes along with the quasi-uniform modes were calculated. The predicted
+spin-waves were imaged in direct space using time resolved scanning
+transmission X-ray microscopy, combined with a ferromagnetic resonance
+excitation scheme (STXM-FMR). STXM-FMR measurements revealed a non-standing
+character of the spin-waves. Also it was shown by micromagnetic simulations and
+confirmed with STXM-FMR results that the observed character of the spin-waves
+can be influenced by the local magnetic fields in different sample geometries.",1911.08281v1
+2018-07-16,Magnetic freezing transition in a CoO/Permalloy bilayer revealed by transverse ac susceptibility,"We utilize variable-temperature, variable-frequency magneto-optical
+transverse magnetic susceptibility technique to study the static and dynamical
+magnetic properties of a thin-film CoO/Permalloy bilayer. Our measurements
+demonstrate that in the studied system, the directional asymmetry of the
+hysteresis loop is associated mainly with the difference in the reversal
+mechanisms between the two reversed states of magnetization stabilized by the
+exchange-induced uniaxial anisotropy. The latter is found to be much larger
+than the exchange-induced unidirectional anisotropy of the ferromagnet. We also
+observe an abrupt variation of the frequency-dependent imaginary part of ac
+susceptibility near the exchange bias blocking temperature, consistent with the
+magnetic freezing transition inferred from the previous time-domain studies of
+magnetic aging in similar systems. The developed measurement approach enables
+precise characterization of the dynamical and static characteristics of
+thin-film magnetic heterostructures that can find applications in
+reconfigurable magnonic and neuromorphic circuits.",1807.05990v2
+2019-10-19,Current-induced spin-orbit field in permalloy interfaced with ultrathin Ti and Cu,"How spin-orbit torques emerge from materials with weak spin-orbit coupling
+(e.g., light metals) is an open question in spintronics. Here, we report on a
+field-like spin-orbit torque (i.e., in-plane spin-orbit field transverse to the
+current axis) in SiO$_2$-sandwiched permalloy (Py), with the top Py-SiO$_2$
+interface incorporating ultrathin Ti or Cu. In both SiO$_2$/Py/Ti/SiO$_2$ and
+SiO$_2$/Py/Cu/SiO$_2$, this spin-orbit field opposes the classical Oersted
+field. While the magnitude of the spin-orbit field is at least a factor of 3
+greater than the Oersted field, we do not observe evidence for a significant
+damping-like torque in SiO$_2$/Py/Ti/SiO$_2$ or SiO$_2$/Py/Cu/SiO$_2$. Our
+findings point to contributions from a Rashba-Edelstein effect or spin-orbit
+precession at the (Ti, Cu)-inserted interface.",1910.08669v2
+2018-02-13,Micromagnetic evaluation of the dissipated heat in cylindrical magnetic nanowires,"Magnetic nanowires (NW) are promising candidates for heat generation under
+AC-field application due to their large shape anisotropy. They may be used for
+catalysis, hyperthermia or water purification treatments. In the present work
+we theoretically evaluate the heat dissipated by a single magnetic nanowire,
+originated from the domain wall dynamics under the action of an AC-field. We
+compare the Permalloy NWs (which demagnetize via the transverse wall
+propagation) with the Co fcc NWs whose reversal mode is via a vortex domain
+wall. The average hysteresis loop areas -which are proportional to the Specific
+Absorption Rate (SAR)- as a function of the field frequency have a pronounced
+maximum in the range 200MHz-1GHz. This maximum frequency is smaller in
+Permalloy than in Co and depends on the nanowire length. A simple model related
+to the nucleation and propagation time and domain wall velocity (higher for the
+vortex than for the transverse domain wall) is proposed to explain the
+non-monotonic SAR dependence on the frequency.",1802.04709v1
+2018-02-18,Scaling of nonlinear susceptibilities in artificial permalloy honeycomb lattice,"Two-dimensional artificial magnetic honeycomb lattice is predicted to
+manifest thermodynamic phase transition to the spin solid order ground state at
+low temperature. Nonlinear susceptibilities are very sensitive to thermodynamic
+phase transition. We have performed the analysis of nonlinear susceptibility to
+explore the thermodynamic nature of spin solid phase transition in artificial
+honeycomb lattice of ultra-small connected permalloy (Ni$_{0.81}$Fe$_{0.19}$)
+elements, typical length of $\simeq$ 12 nm. The nonlinear susceptibility,
+$\chi_{n1}$, is found to exhibit an unusual cross-over character in both
+temperature and magnetic field. The higher order susceptibility $\chi_3$
+changes from positive to negative as the system traverses through the spin
+solid phase transition at $T_s$ = 29 K. Additionally, the static critical
+exponents, used to test the scaling of $\chi_{n1}$, do not follow the
+conventional scaling relation. We conclude that the transition to the ground
+state is not truly thermodynamic, thus raises doubt about the validity of
+predicted zero entropy state in the spin solid phase.",1802.06325v1
+2020-05-15,Direct imaging of the ac component of the pumped spin polarization with element specificity,"Spin pumping in a ferromagnet/nonferromagnet heterostructure is directly
+imaged with spatial resolution as well as element selectivity. The
+time-resolved detection in scanning transmission x-ray microscopy allows to
+directly probe the spatial extent of the ac spin polarization in Co-doped ZnO
+which is generated by spin pumping from an adjacent permalloy microstrip.
+Comparing the relative phases of the dynamic magnetization component of the two
+constituents is possible and found to be antiphase. The correlation between the
+distribution of the magnetic excitation in the permalloy and the Co-doped ZnO
+reveals that laterally there is no one-to-one correlation. The observed
+distribution is rather complex, but integrating over larger areas clearly
+demonstrates that the spin polarization in the nonferromagnet extends laterally
+beyond the region of the ferromagnetic microstrip. Therefore the observations
+are better explained by a local spin pumping efficieny and a lateral
+propagation of the ac spin polarization in the nonferromagnet over the range of
+a few micrometers.",2005.08728v1
+2016-03-17,Spin wave amplification using the spin Hall effect in permalloy/platinum bilayers,"We investigate the effect of an electrical current on the attenuation length
+of a 900 nm wavelength spin-wave in a permalloy/Pt bilayer using propagating
+spin-wave spectroscopy. The modification of the spin-wave relaxation rate is
+linear in current density, reaching up to 14% for a current density of
+2.3$\times10^{11} $A/m$^2$ in Pt. This change is attributed to the spin
+transfer torque induced by the spin Hall effect and corresponds to an effective
+spin Hall angle of 0.13, which is among the highest values reported so far. The
+spin Hall effect thus appears as an efficient way of amplifying/attenuating
+propagating spin waves.",1603.05478v1
+2017-02-09,Long-range proximity effect in Nb-based heterostructures induced by a magnetically inhomogeneous permalloy layer,"Odd-frequency triplet Cooper pairs are believed to be the carriers of
+long-range superconducting correlations in ferromagnets. Such triplet pairs are
+generated by inhomogeneous magnetism at the interface between a superconductor
+(S) and a ferromagnet (F). So far, reproducible long-range effects were
+reported only in complex layered structures designed to provide the magnetic
+inhomogeneity. Here we show that spin triplet pair formation can be found in
+simple unstructured Nb/Permalloy (Py = Ni_0.8Fe_0.2)/Nb trilayers and Nb/Py
+bilayers, but only when the thickness of the ferromagnetic layer ranges between
+140 and 250 nm. The effect is related to the emergence of an intrinsically
+inhomogeneous magnetic state, which is a precursor of the well-known stripe
+regime in Py that in our samples sets in at thickness larger than 300 nm.",1702.02765v1
+2017-02-10,"Relative weight of the inverse spin Hall and spin rectification effects for metallic Py,Fe/Pt and insulating YIG/Pt bilayers estimated by angular dependent spin pumping measurements","We quantify the relative weight of inverse spin Hall and spin rectification
+effects occurring in RF-sputtered polycrystalline permalloy, molecular beam
+epitaxy-grown epitaxial iron and liquid phase epitaxy-grown yttrium-iron-garnet
+bilayer systems with different capping materials. To distinguish the spin
+rectification signal from the inverse spin Hall voltage the external magnetic
+field is rotated in-plane to take advantage of the different angular
+dependencies of the prevailing effects. We prove that in permalloy anisotropic
+magnetoresistance is the dominant source for spin rectification while in
+epitaxial iron the anomalous Hall effect has an also comparable strength. The
+rectification in yttrium-iron-garnet/platinum bilayers reveals an angular
+dependence imitating the one seen for anisotropic magnetoresistance caused by
+spin Hall magnetoresistance.",1702.03119v1
+2017-06-10,Spin wave nonreciprocity and magnonic band structure in thin permalloy film induced by dynamical coupling with an array of Ni stripes,"An efficient way for the control of spin wave propagation in a magnetic
+medium is the use of periodic patterns known as magnonic crystals (MCs).
+However, the fabrication of MCs especially bi-components, with periodicity on
+nanoscale, is a challenging task due to the requirement for sharp interfaces.
+An alternative method to circumvent this problem is to use homogeneous
+ferromagnetic film with modified periodically surrounding. The structure is
+also suitable for exploiting nonreciprocal properties of the surface spin
+waves. In this work, we demonstrate that the magnonic band structure forms in
+thin permalloy film due to dynamical magnetostatic coupling with Ni stripes
+near its surface. We show, that the band gap width can be systematically tuned
+by the changing interlayer thickness between film and stripes. We show also the
+effect of nonreciprocity, which is seen at the band gap edge shifted from the
+Brillouin zone boundary and also in nonreciprocal interaction of propagating
+spin waves in Py film with the standing spin waves in Ni stripes. Our findings
+open possibility for further investigation and exploitation of the
+nonreciprocity and band structure in magnonic devices.",1706.03202v1
+2017-10-03,Synchronous magnetic control of water droplets in bulk ferrofluid,"We present a microfluidic platform for two-dimensional manipulation of water
+droplets immersed in bulk oil-based ferrofluid. Although non-magnetic, the
+droplets are exclusively controlled by magnetic fields, without any
+pressure-driven flow. The diphasic fluid layer is trapped in a submillimeter
+Hele-Shaw chamber that includes permalloy tracks on its substrate. An in-plane
+rotating magnetic field magnetizes the permalloy tracks, thus producing local
+magnetic gradients, while an orthogonal magnetic field magnetizes the bulk
+ferrofluid. To minimize the magnetostatic energy of the system, droplets are
+attracted towards the locations of the tracks where ferrofluid is repelled.
+Using this technique, we demonstrate synchronous generation and propagation of
+water droplets, analyze PIV data of the bulk ferrofluid flow and study the
+kinematics of propagation. In addition, we show controlled break-up of droplets
+and droplet-to-droplet interactions. Finally, we discuss future applications
+owing to the potential biocompatibility of the droplets.",1710.00961v2
+2019-03-13,Spin wave stiffness and exchange stiffness of doped permalloy via ab-initio calculation,"The way doping affects the spin wave stiffness and the exchange stiffness of
+permalloy (Py) is investigated via ab-initio calculations, using the
+Korringa-Kohn-Rostoker (KKR) Green function formalism. By considering various
+types of dopants of different nature (V, Gd, and Pt), we are able to draw
+general conclusions. To describe the trends of the stiffness with doping is it
+sufficient to account for the exchange coupling between nearest neighbors. The
+polarizability of the impurities is not an important factor for the spin wave
+stiffness. Rather, the decisive factor is the hybridization between the
+impurity and the host states as reflected by changes in the Bloch spectral
+function. Our theoretical results agree well with earlier experiments.",1903.05506v2
+2019-03-19,Study of magnetization reversal in Neel and Bloch regime of Ni and Py stripes using Kerr microscopy,"We present a systematic study of the magnetization reversal of nickel and
+permalloy micro-stripes with Neel and Bloch domain walls using Kerr microscopy.
+Magnetic field driven domain propagation was observed from higher width to
+lower width stripes for magnetic fields applied along the length of
+micro-stripes. Stripe like domains were observed with nucleation starting in
+lower width region followed by their propagation to higher width regions for
+magnetic fields applied along the width of micro-stripes. The comparison of
+magnetization reversal in Bloch and N\'eel domain wall regime showed higher
+domain wall density in Bloch regime for both nickel and permalloy stripes.",1903.08106v3
+2019-08-23,Massively parallel atomistic simulation of ultrafast thermal spin dynamics of a permalloy vortex,"Ultrafast magnetization dynamics probes the most fundamental properties of
+magnetic materials, exploring questions about the fundamental interactions
+responsible for magnetic phenomena. Thermal effects are known to be extremely
+important for laser-induced dynamics in metallic systems, but the dynamics of
+topological magnetic structures are little understood. Here we apply a
+massively parallel atomistic spin dynamics simulation to study the response of
+a permalloy vortex to a 50 fs laser pulse. We find that macroscopically the
+short timescale dynamics are indistinguishable from the bulk, but that strong
+edge spin waves lead to a complex time evolution of the magnetic structure and
+long-lived oscillations on the nanosecond timescale. In the near future such
+simulations will provide unprecedented insight into the dynamics of magnetic
+materials and devices beyond the approximations of continuum micromagnetics.",1908.08885v1
+2019-09-13,Transport properties of doped permalloy via ab-initio calculations: effect of the host disorder,"Transport properties of permalloy doped with V, Co, Pt, and Au are explored
+via ab-initio calculations. The Kubo-Bastin formula is evaluated within the
+fully relativistic Korringa-Kohn-Rostoker Green function formalism. Finite
+temperature effects are treated by means of the alloy analogy model. It is
+shown that the fact that the host is disordered and not crystalline has a
+profound effect on how the conductivities characterizing the anomalous Hall
+effect and the spin Hall effect depend on the dopant concentration. Several
+relationships between quantities characterizing charge and spin transport are
+highlighted. The decrease of the longitudinal charge conductivity with
+increasing doping depends on the dopant type, following the sequence
+Co-Au-Pt-V. The dependence of the anomalous Hall and spin Hall conductivities
+on the dopant concentration is found to be non-monotonic. Introducing a finite
+temperature changes the overall trends significantly. The theoretical results
+are compared with available experimental data.",1909.06066v3
+2019-09-27,Thermally driven two-magnet nano-oscillator with large spin-charge conversion,"Next-generation spintronic applications require material properties that can
+be hardly met by one material candidate. Here we demonstrate that by combining
+insulating and metallic magnets, enhanced spin-charge conversion and
+energy-efficient thermal spin currents can be realized. We develop a nanowire
+device consisting of an yttrium iron garnet and permalloy bi-layer. An
+interfacial temperature gradient drives the nanowire magnetization into
+auto-oscillations at gigahertz frequencies. Interfacial spin coupling and
+magnetoresistance of the permalloy layer translate spin dynamics into sizable
+microwave signals. The results show prospect for energy-efficient spintronic
+devices and present an experimental realization of magnon condensation in a
+heterogeneous magnetic system.",1909.12445v1
+2019-12-31,Probing magnon-magnon coupling in exchange coupled Y$_3$Fe$_5$O$_{12}$/Permalloy bilayers with magneto-optical effects,"We demonstrate the magnetically-induced transparency (MIT) effect in
+Y$_3$Fe$_5$O$_{12}$(YIG)/Permalloy(Py) coupled bilayers. The measurement is
+achieved via a heterodyne detection of the coupled magnetization dynamics using
+a single wavelength that probes the magneto-optical Kerr and Faraday effects of
+Py and YIG, respectively. Clear features of the MIT effect are evident from the
+deeply modulated ferromagnetic resonance of Py due to the
+perpendicular-standing-spin-wave of YIG. We develop a phenomenological model
+that nicely reproduces the experimental results including the induced amplitude
+and phase evolution caused by the magnon-magnon coupling. Our work offers a new
+route towards studying phase-resolved spin dynamics and hybrid magnonic
+systems.",1912.13407v2
+2020-02-29,Nonreciprocal Emergence of Hybridized Magnons in magnetic thin Films,"We investigate the transfer and control of nonreciprocity through magnons
+themselves in permalloy thin films deposited on surface oxide silicon
+substrate. Evidences of nonreciprocal emergence of hybridized dipole exchange
+magnons (spin waves) at two permalloy surfaces are provided by studying magnon
+transmission and asymmetry, via Brillouin light scattering measurements. The
+dipole dominated spin wave and exchange dominated spin wave are found to be
+localized near the top and bottom surfaces, respectively, and traveling along
+opposite directions. The nonreciprocity and the localization are intertwined
+and ca n be tuned by an in plane magnetic field. The effects are well explained
+by the magnetostatic theory and can be quantitatively reproduced by the
+micromagnetic simulations. Our findings provide a simple and flexible approach
+to nonreciprocal all magnon logi c devices with highly compatible with silicon
+based integrated circuit technology.",2003.00230v4
+2020-07-30,Resonant subwavelength control of the phase of spin waves reflected from a ferromagnetic film edge,"Using frequency-domain finite element calculations cross-checked with
+micromagnetic simulations, we demonstrate that the phase of spin waves
+reflected from an interface between a permalloy film and a bilayer can be
+controlled by changing dimensions of the bilayer. Treating the bilayer formed
+by the permalloy film and a ferromagnetic stripe as a segment of a multi-mode
+waveguide, we show that spin-wave Fabry-Perot resonances of one of its modes
+are responsible for the high sensitivity of the phase of reflected waves to
+stripe width and the stripe-film separation. Thus, the system is a unique
+realization of a fully magnonic Gires-Tournois interferometer based on a
+two-modes resonator, which can be treated as a magnonic counterpart of a
+metasurface, since it enables manipulation of the phase of spin waves at
+subwavelength distances. Knowledge gained from these calculations might be used
+to design magnonic devices such as flat lenses or magnetic particle detectors.",2007.15226v5
+2020-10-09,Inplane spin orbit torque magnetization switching and its detection using the spin rectification effect at sub-GHz frequencies,"Inplane magnetization reversal of a permalloy/platinum bilayer was detected
+using the spin rectification effect. Using a sub GHz microwave frequency to
+excite spin torque ferromagnetic resonance (ST FMR) in the bilayer induces two
+discrete DC voltages around an external static magnetic field of 0 mT. These
+discrete voltages depend on the magnetization directions of the permalloy and
+enable detection of the inplane magnetization reversal. The threshold current
+density for the magnetization reversal is from 10 to 20 MA/cm^2, the same order
+as for known spin orbit torque (SOT) switching with in-plane magnetization
+materials. The magnitude of the signal is the same or larger than that of the
+typical ST FMR signal; that is, detection of magnetization switching is highly
+sensitive in spite of deviation from the optimal ST-FMR condition. The proposed
+method is applicable to a simple device structure even for a small
+ferromagnetic electrode with a width of 100 nm.",2010.04435v1
+2021-06-18,Exchange bias without directional anisotropy in Permalloy/CoO bilayers,"We utilize transverse ac susceptibility measurements to characterize magnetic
+anisotropy in archetypal exchange-bias bilayers of ferromagnet Permalloy (Py)
+and antiferromagnet CoO. Unidirectional anisotropy is observed for thin Py, but
+becomes negligible at larger Py thicknesses, even though the directional
+asymmetry of the magnetic hysteresis loop remains significant. Additional
+magnetoelectronic measurements, magneto-optical imaging, as well as
+micromagnetic simulations show that these surprising behaviors are likely
+associated with asymmetry of spin flop distribution created in CoO during Py
+magnetization reversal, which facilitates the rotation of the latter back into
+its field-cooled direction. Our findings suggest new possibilities for
+efficient realization of multistable nanomagnetic systems for neuromorphic
+applications.",2106.09924v1
+2021-11-09,Design of soft magnetic materials,"We present a strategy for the design of ferromagnetic materials with
+exceptionally low magnetic hysteresis, quantified by coercivity. In this
+strategy, we use a micromagnetic algorithm that we have developed in previous
+research and which has been validated by its success in solving the ""Permalloy
+Problem"" -- the well-known difficulty of predicting the composition 78.5% Ni of
+lowest coercivity in the Fe-Ni system -- and by the insight, it provides into
+the ""Coercivity Paradox"" of W. F. Brown. Unexpectedly, the design strategy
+predicts that cubic materials with large saturation magnetization $m_s$ and
+large magnetocrystalline anisotropy constant $\kappa_1$ will have low
+coercivity on the order of that of Permalloy, as long as the magnetostriction
+constants $\lambda_{100}, \lambda_{111}$ are tuned to special values. The
+explicit prediction for a cubic material with low coercivity is the
+dimensionless number $(c_{11}-c_{12}) \lambda_{100}^2/\kappa_1 = 81$ for
+$\langle 100 \rangle$ easy axes. The results would seem to have a broad
+potential application, especially to magnetic materials of interest in energy
+research.",2111.05456v1
+2022-10-06,Field and temperature tuning of magnetic diode in permalloy honeycomb lattice,"The observation of magnetic diode behavior with ultra-low forward voltage of
+5 mV renders new venue for energetically efficient spintronic device research
+in the unconventional system of two-dimensional permalloy honeycomb lattice.
+Detailed understanding of temperature and magnetic field tuning of diode
+behavior is imperative to any practical application. Here, we report a
+comprehensive study in this regard by performing electrical measurements on
+magnetic diode sample as functions of temperature and magnetic field. Magnetic
+diode is found to persist across the broad temperature range. Magnetic field
+application unveils a peculiar reentrant characteristic where diode behavior is
+suppressed in remnant field but reappears after warming to room temperature.
+Analysis of I-V data suggests a modest energy gap, 0.03-0.1 eV, which is
+comparable to magnetic Coulomb's interaction energy between emergent magnetic
+charges on honeycomb vertices in the reverse biased state. It affirms the role
+of magnetic charge correlation in unidirectional conduction in 2D honeycomb
+lattice. The experimental results are expected to pave way for the utilization
+of magnetic diode in next generation spintronic device applications.",2210.03184v1
+2023-01-21,"Soft X-ray spectro-ptychography on boron nitride nanotubes, carbon nanotubes and permalloy nanorods","Spectro-ptychography offers improved spatial resolution and additional phase
+spectral information relative to that provided by scanning transmission X-ray
+microscopes (STXM). However, carrying out ptychography at the lower range of
+soft X-ray energies (e.g., below 200 eV to 600 eV) on samples with weakly
+scattering signals can be challenging. We present soft X-ray ptychography
+results at energies as low as 180 eV and illustrate the capabilities with
+results from permalloy nanorods (Fe 2p), carbon nanotubes (C 1s), and boron
+nitride bamboo nanostructures (B 1s, N1s). We describe optimization of low
+energy X-ray spectro-ptychography and discuss important challenges associated
+with measurement approaches, reconstruction algorithms, and their effects on
+the reconstructed images. A method for evaluating the increase in radiation
+dose when using overlapping sampling is presented.",2301.08982v1
+2023-07-18,Ultrafast spin-to-charge conversions of antiferromagnetic (111)-oriented $\mathrm{L1_2}$-$\mathrm{Mn_3Ir}$,"Antiferromagnetic $\mathrm{L1_2}$-$\mathrm{Mn_3Ir}$ combines outstanding
+spin-transport properties with magnons in the terahertz (THz) frequency range.
+However, the THz radiation emitted by ultrafast spin-to-charge conversion via
+the inverse spin Hall effect remains unexplored. In this study, we measured the
+THz emission and transmission of a permalloy/(111)-oriented
+$\mathrm{L1_2}$-$\mathrm{Mn_3Ir}$ multilayer by THz time-domain spectroscopy.
+The spin Hall angle was determined to be approximately constant at 0.035 within
+a frequency range of 0.3-2.2 THz, in comparison with the THz spectroscopy of a
+permalloy/Pt multilayer. Our results not only demonstrate the potential of
+$\mathrm{L1_2}$-$\mathrm{Mn_3Ir}$ as a spintronic THz emitter but also provide
+insights into the THz spin transport properties of
+$\mathrm{L1_2}$-$\mathrm{Mn_3Ir}$.",2307.08928v3
+2024-02-22,Unraveling the origin of antiferromagnetic coupling at YIG/permalloy interface,"We investigate the structural and electronic origin of antiferromagnetic
+coupling in the Yttrium iron garnet (YIG) and permalloy (Py) bilayer system at
+the atomic level. Ferromagnetic Resonance (FMR) reveal unique hybrid modes in
+samples prepared with surface ion milling, indicative of antiferromagnetic
+exchange coupling at the YIG/Py interface. Using scanning transmission electron
+microscopy (STEM), we highlight significant interfacial differences introduced
+by ion-milling. The observations suggests that the antiferromagnetic coupling
+in YIG/Py bilayers is predominantly driven by an oxygen-mediated super-exchange
+coupling mechanism on the tetrahedral Fe terminated YIG surface, which is
+supported by density functional theory (DFT) calculations. This research
+provides critical insight into the fundamental mechanisms governing the
+efficiency of coupling in magnetic bilayers and underscores the pivotal role of
+oxide surface termination in modulating magnetic interfacial dynamics.",2402.14553v2
+2021-07-22,Interfacial Spin-Orbit Torques and Magnetic Anisotropy in WSe$_{2}$/Permalloy Bilayers,"Transition metal dichalcogenides (TMDs) are promising materials for efficient
+generation of current-induced spin-orbit torques on an adjacent ferromagnetic
+layer. Numerous effects, both interfacial and bulk, have been put forward to
+explain the different torques previously observed. Thus far, however, there is
+no clear consensus on the microscopic origin underlying the spin-orbit torques
+observed in these TMD/ferromagnet bilayers. To shine light on the microscopic
+mechanisms at play, here we perform thickness dependent spin-orbit torque
+measurements on the semiconducting WSe$_{2}$/permalloy bilayer with various
+WSe$_{2}$ layer thickness, down to the monolayer limit. We observe a large
+out-of-plane field-like torque with spin-torque conductivities up to
+$1\times10^4 ({\hbar}/2e) ({\Omega}m)^{-1}$. For some devices, we also observe
+a smaller in-plane antidamping-like torque, with spin-torque conductivities up
+to $4\times10^{3} ({\hbar}/2e) ({\Omega}m)^{-1}$, comparable to other TMD-based
+systems. Both torques show no clear dependence on the WSe$_{2}$ thickness, as
+expected for a Rashba system. Unexpectedly, we observe a strong in-plane
+magnetic anisotropy - up to about $6.6\times10^{4} erg/cm^{3}$ - induced in
+permalloy by the underlying hexagonal WSe$_{2}$ crystal. Using scanning
+transmission electron microscopy, we confirm that the easy axis of the magnetic
+anisotropy is aligned to the armchair direction of the WSe$_{2}$. Our results
+indicate a strong interplay between the ferromagnet and TMD, and unveil the
+nature of the spin-orbit torques in TMD-based devices. These findings open new
+avenues for possible methods for optimizing the torques and the interaction
+with interfaced magnets, important for future non-volatile magnetic devices for
+data processing and storage.",2107.10621v2
+2001-09-17,Ferromagnetic resonance in periodic particle arrays,"We report measurements of the ferromagnetic resonance (FMR) spectra of arrays
+of submicron size periodic particle arrays of permalloy produced by
+electron-beam lithography. In contrast to plane ferromagnetic films, the
+spectra of the arrays show a number of additional resonance peaks, whose
+position depends strongly on the orientation of the external magnetic field and
+the interparticle interaction. Time-dependent micromagnetic simulation of the
+ac response show that these peaks are associated with coupled exchange and
+dipolar spin wave modes",0109307v1
+2001-10-11,Enhanced Gilbert Damping in Thin Ferromagnetic Films,"Using a scattering matrix approach, the precession of the magnetization of a
+ferromagnet is shown to transfer spins into adjacent normal metal layers. This
+``pumping'' of spins slows down the precession corresponding to an enhanced
+Gilbert damping factor in the Landau-Lifshitz equation. The damping is
+expressed in terms of the scattering matrix of the ferromagnet-normal metal
+interface, which is accessible to model and first-principles calculations. Our
+estimates for permalloy thin films explain the trends observed in recent
+experiments.",0110247v2
+2002-01-04,Magnon modes for thin circular vortex state magnetic dot,"The magnetization in a magnetic microdot made from soft magnetic materials
+can have a vortex-like ground state structure resulting from competition
+between the exchange and dipolar interactions. Normal mode magnon frequencies
+for such dots are calculated taking into account both exchange and
+magnetostatic effects. The presence of a low-lying mode as well as doublet
+structure with small splitting is demonstrated. Estimates of the mode
+frequencies for permalloy dots are obtained, and the possibility of
+experimental detection of such modes is discussed.",0201050v1
+2003-04-14,Switching a spin-valve back and forth by current-induced domain wall motion,"We have studied the current-induced displacement of a domain wall (DW) in the
+permalloy (Py) layer of a Co/Cu/Py spin valve structure at zero and very small
+applied field. The displacement is in opposite direction for opposite dc
+currents, and the current density required to move DW is only of the order of
+10^6 A/cm^2. For H = 3 Oe, a back and forth DW motion between two stable
+positions is observed. We also discuss the effect of an applied field on the DW
+motion.",0304312v1
+2003-12-02,Studies of dc Current-Driven Switching in Py/N/Py magnetic nanopillars,"We provide new data on current-driven switching in Permalloy (Py = Ni84Fe16)
+based nanopillars at room temperature and 4.2K that confirm and extend
+previously published work. We present data for both uncoupled and
+antiferromagnetically coupled samples. The latter confirm prior results for
+Co/Cu/Co. We show that inserting sufficiently strong spin-flip-scattering into
+the Cu layer eliminates hysteretic current-driven switching. This result may
+have ramifications for understanding current-driven switching.",0312078v1
+2004-04-13,Spin filtering in a hybrid ferromagnetic-semiconductor microstructure,"We fabricated a hybrid structure in which cobalt and permalloy micromagnets
+produce a local in-plane spin-dependent potential barrier for high-mobility
+electrons at the GaAs/AlGaAs interface. Spin effects are observed in ballistic
+transport in the tens' millitesla range of the external field, and are
+attributed to switching between Zeeman and Stern-Gerlach modes -- the former
+dominating at low electron densities.",0404282v1
+2004-08-27,Tunable magnetization damping in transition metal ternary alloys,"We show that magnetization damping in Permalloy, Ni80Fe20 (``Py''), can be
+enhanced sufficiently to reduce post-switching magnetization precession to an
+acceptable level by alloying with the transition metal osmium (Os). The damping
+increases monotonically upon raising the Os-concentration in Py, at least up to
+9% of Os. Other effects of alloying with Os are suppression of magnetization
+and enhancement of in-plane anisotropy. Magnetization damping also increases
+significantly upon alloying with the five other transition metals included in
+this study (4d-elements: Nb, Ru, Rh; 5d-elements: Ta, Pt) but never as strongly
+as with Os.",0408608v1
+2005-06-24,New Memory Concept for Superconducting Electronics,"A new concept for nonvolatile superconducting memories is proposed. The
+devices combine ferromagnetic dots for the storage of the data and Josephson
+junctions for their readout. Good scalability is expected for large scale
+integration. First memory cells have been implemented using 3
+$\mu$m-Nb-technology and permalloy dots. Nonvolatile data storage at 300 K was
+demonstrated.",0506647v2
+2005-10-21,Magnetic Vortex Core Dynamics in a Ferromagnetic Dot,"We report direct imaging by means of x-ray photoemission electron microscopy
+of the dynamics of magnetic vortices confined in micron-size circular Permalloy
+dots that are 30 nm thick. The vortex core positions oscillate on a 10-ns
+timescale in a self-induced magnetostatic potential well after the in-plane
+magnetic field is turned off. The measured oscillation frequencies as a
+function of the aspect ratio (thickness/radius) of the dots are in agreement
+with theoretical calculations presented for the same geometry.",0510595v1
+2005-11-02,Current-induced vortex displacement and annihilation in a single Permalloy disk,"The induced motion of a magnetic vortex in a micron-sized ferromagnetic disk
+due to the DC current injection is studied by measuring planar Hall effect. The
+DC current injection is found to induce the spin torque that sweeps the vortex
+out of the disk at the critical current while bias magnetic field are applied.
+The current-induced vortex core displacement deduced from the change in planar
+Hall resistance is quantitatively consistent with theoretical prediction. Peak
+structures similar to those originated from spin wave excitations are observed
+in the differential planar Hall resistance curve.",0511040v1
+2006-06-07,Ferromagnetic relaxation by magnon-induced currents,"A theory for calculating spin wave relaxation times based on the
+magnon-electron interaction is developed. The theory incorporates a thin film
+geometry and is valid for a large range of magnon frequencies and wave vectors.
+For high conductivity metals such as permalloy, the wave vector dependent
+damping constant approaches values as high as 0.2, showing the large magnitude
+of the effect, and can dominate experimentally observed relaxation.",0606197v1
+2006-06-21,Current-excited magnetization dynamics in narrow ferromagnetic wires,"We investigate the current-excited magnetization dynamics in a narrow
+ferromagnetic Permalloy wire by means of Lorentz microscopy, together with the
+results of simultaneous transport measurements. A detailed structural evolution
+of the magnetization is presented as a function of the applied current density.
+Local structural deformation, bidirectional displacement, and magnetization
+reversal are found below the Curie temperature with increasing the current
+density. We discuss probable mechanisms of observed features of the
+current-excited magnetization dynamics.",0606547v1
+2006-07-03,On-chip detection of ferromagnetic resonance of a single submicron permalloy strip,"We measured ferromagnetic resonance of a single submicron ferromagnetic
+strip, embedded in an on-chip microwave transmission line device. The method
+used is based on detection of the oscillating magnetic flux due to the
+magnetization dynamics, with an inductive pick-up loop. The dependence of the
+resonance frequency on applied static magnetic field agrees very well with the
+Kittel formula, demonstrating that the uniform magnetization precession mode is
+being driven.",0607036v1
+2006-08-10,Spin Dynamics of a Magnetic Antivortex,"We report on a study of the dynamics of a magnetic antivortex in a submicron,
+asteroid shaped, permalloy ferromagnet using micromagnetic simulations. As with
+vortex states in disk and square geometries, a gyrotropic mode was found in
+which a shifted antivortex core orbits about the center of the asteroid. Pulsed
+magnetic fields were used to generate azimuthal or radial spin wave modes,
+depending on the field orientation. The degeneracy of low frequency azimuthal
+mode frequencies is lifted by gyrotropic motion of the antivortex core, and
+restored by inserting a hole in the center of the particle to suppress this
+motion. We briefly compare the dynamics of the vortex state of the asteroid to
+the antivortex. The size dependence of the antivortex modes is reported.",0608245v1
+2006-09-08,Large cone angle magnetization precession of an individual nanomagnet with dc electrical detection,"We demonstrate on-chip resonant driving of large cone-angle magnetization
+precession of an individual nanoscale permalloy element. Strong driving is
+realized by locating the element in close proximity to the shorted end of a
+coplanar strip waveguide, which generates a microwave magnetic field. We used a
+microwave frequency modulation method to accurately measure resonant changes of
+the dc anisotropic magnetoresistance. Precession cone angles up to $9^{0}$ are
+determined with better than one degree of resolution. The resonance peak shape
+is well-described by the Landau-Lifshitz-Gilbert equation.",0609190v1
+2006-10-09,Single-domain versus two-domain configuration in thin ferromagnetic prisms,"Thin ferromagnetic elements in the form of rectangular prisms are
+theoretically investigated in order to study the transition from single-domain
+to two-domain state, with changing the in-plane aspect ratio p. We address two
+main questions: first, how general is the transition; second, how the critical
+value p_c depends on the physical parameters. We use two complementary methods:
+discrete-lattice calculations and a micromagnetic continuum approach. Ultrathin
+films do not appear to split in two domains. Instead, thicker films may undergo
+the above transition. We have used the continuum approach to analyze recent
+Magnetic Force Microscopy observations in 30 nm-thick patterned Permalloy
+elements, finding a good agreement for p_c.",0610233v1
+2006-11-25,Dynamics of Vortex Core Switching in Ferromagnetic Nanodisks,"Dynamics of magnetic vortex core switching in nanometer-scale permalloy disk,
+having a single vortex ground state, was investigated by micromagnetic
+modeling. When an in-plane magnetic field pulse with an appropriate strength
+and duration is applied to the vortex structure, additional two vortices, i.e.,
+a circular- and an anti-vortex, are created near the original vortex core.
+Sequentially, the vortex-antivortex pair annihilates. A spin wave is created at
+the annihilation point and propagated through the entire element; the relaxed
+state for the system is the single vortex state with a switched vortex core.",0611640v1
+2007-12-17,Proximity effect-assisted absorption of spin currents in superconductors,"The injection of pure spin current into superconductors by the dynamics of a
+ferromagnetic contact is studied theoretically. Taking into account suppression
+of the order parameter at the interfaces (inverse proximity effect) and the
+energy-dependence of spin-flip scattering, we determine the
+temperature-dependent ferromagnetic resonance linewidth broadening. Our results
+agree with recent experiments in Nb|permalloy bilayers [C. Bell et al.,
+arXiv:cond-mat/0702461].",0712.2814v1
+2008-09-26,Domain wall displacement in Py square ring for single nanometric magnetic bead detection,"A new approach based on the domain wall displacement in confined
+ferromagnetic nanostructures for attracting and sensing a single nanometric
+magnetic particles is presented. We modeled and experimentally demonstrated the
+viability of the approach using an anisotropic magnetoresistance device made by
+a micron-size square ring of Permalloy designed for application in magnetic
+storage. This detection concept can be suitable to biomolecular recognition,
+and in particular to single molecule detection.",0809.4649v1
+2008-12-02,Independent magnetization behavior of a ferromagnetic metal/semiconductor hybrid system,"We report the discovery of an effect where two ferromagnetic materials, one
+semiconductor ((Ga,Mn)As) and one metal (permalloy), can be directly deposited
+on each other and still switch their magnetization independently. We use this
+independent magnetization behavior to create various resistance states
+dependent on the magnetization direction of the individual layers. At zero
+magnetic field a two layer device can reach up to four non-volatile resistance
+states.",0812.0455v1
+2009-01-13,Refractive index and Snell's Law for Dipolar-Exchange Spin-Waves in a Confined Planar Structure,"We derived the analytical forms of refractive index and Snell law for
+dipolar-exchange spin waves of reflection and refraction at a magnetically
+heterogeneous interface in a geometrically confined planer structure composed
+of different magnetic thin films from a microscopic scattering approach. A
+novel behavior, the optical total reflection, was demonstrated for spin waves
+with a specific interface between Yttrium iron garnet (Y3Fe5O12) and Permalloy
+(Ni80Fe20), by analytical and micromagnetic numerical calculations.",0901.1700v2
+2009-01-15,Vortex stabilization in magnetic trilayer dots,"The magnetization reversal and spin structure in circular
+Co/insulator/Ni80Fe20 trilayer dots has been investigated numerically. The
+effect of dipolar coupling between a soft ferromagnetic Permalloy (Py=Ni80Fe20)
+layer and a hard ferromagnetic Cobalt layer inside one stack is studied. We
+find either a stabilization or even a triggering of the vortex state in the Py
+layer due to the magnetic stray field of the Co layer, while the Co
+magnetization remains in a single-domain state. Furthermore, for thin Py layers
+a 360 deg-domain wall is observed. We construct a phase diagram, where regions
+of vortex stabilization, triggering, and occurrence of a 360 deg domain wall
+are marked.",0901.2209v1
+2009-04-06,Characterisation of Ferromagnetic Contacts to Carbon Nanotubes,"We present an investigation of different thin-film evaporated ferromagnetic
+materials for their suitability as electrodes in individual single-wall and
+multi-wall carbon nanotube-based spin devices. Various electrode shapes made
+from permalloy (Ni_{81}Fe_{19}), the diluted ferromagnet PdFe, and PdFe/Fe
+bilayers are studied for both their micromagnetic properties and their contact
+formation to carbon nanotubes. Suitable devices are tested in low-temperature
+electron transport measurements, displaying the typical tunneling
+magnetoresistance of carbon nanotube pseudo spin valves.",0904.0907v2
+2009-08-14,Spin-wave interference in three-dimensional rolled-up ferromagnetic microtubes,"We have investigated spin-wave excitations in rolled-up Permalloy microtubes
+using microwave absorption spectroscopy. We find a series of quantized
+azimuthal modes which arise from the constructive interference of Damon-Eshbach
+type spin waves propagating around the circumference of the microtubes, forming
+a spin-wave resonator. The mode spectrum can be tailored by the tube's radius
+and number of rolled-up layers.",0908.2082v1
+2009-10-14,Surface spin flip probability of mesoscopic Ag wires,"Spin relaxation in mesoscopic Ag wires in the diffusive transport regime is
+studied via nonlocal spin valve and Hanle effect measurements performed on
+permalloy/Ag lateral spin valves. The ratio between momentum and spin
+relaxation times is not constant at low temperatures. This can be explained
+with the Elliott-Yafet spin relaxation mechanism by considering the momentum
+surface relaxation time as being temperature dependent. We present a model to
+separately determine spin flip probabilities for phonon, impurity and surface
+scattering and find that the spin flip probability is highest for surface
+scattering.",0910.2744v3
+2009-11-13,Nano-Torsional Resonator Torque Magnetometry,"Magnetic torque is used to actuate nano-torsional resonators, which are
+fabricated by focused-ion-beam milling of permalloy coated silicon nitride
+membranes. Optical interferometry is used to measure the mechanical response of
+two torsion modes at resonance, which is proportional to the magnetization
+vector of the nanomagnetic volume. By varying the bias magnetic field, the
+magnetic behavior can be measured with excellent sensitivity ($\approx 10^8
+\mu_B$) for single magnetic elements.",0911.2517v2
+2010-04-15,Ground-state configurations in ferromagnetic nanotori,"Magnetization ground states are studied in toroidal nanomagnets. The
+energetics associated to the ferromagnetic, vortex and onion-like
+configurations are explicitly computed. The analysis reveals that the vortex
+appears to be the most prominent of such states, minimizing total energy in
+every torus with internal radius $r\gtrsim10\,{\rm nm}$ (for Permalloy). For
+$r\lesssim10\,{\rm nm}$ the vortex remains the most favorable pattern whenever
+$R/\ell_{ex}\gtrsim1.5$ ($R$ is the torus external radius and $\ell_{ex}$ is
+the exchange length), being substituted by the ferromagnetic state whenever
+$R/\ell_{ex}\lesssim1.5$.",1004.2689v1
+2010-12-18,Conduction Electron Spin-Flipping at Sputtered Co(90)Fe(10)/Cu Interfaces,"From measurements of the current-perpendicular-to-plane (CPP)
+magnetoresistance of ferromagnetically coupled [Co(90)Fe(10)/Cu]xn multilayers,
+within sputtered Permalloy-based double exchange biased spin-valves, we
+determine the parameter delta[(Co(90)Fe(10))/Cu] = 0.19 +/- 0.04 that sets the
+probability P of spin-flipping at a Co(90)Fe(10)/Cu interface via the equation
+P = 1 - exp(-delta).",1012.4099v1
+2011-08-05,Thermoelectric detection of ferromagnetic resonance of a nanoscale ferromagnet,"We present thermoelectric measurements of the heat dissipated due to
+ferromagnetic resonance of a Permalloy strip. A microwave magnetic field,
+produced by an on-chip coplanar strip waveguide, is used to drive the
+magnetization precession. The generated heat is detected via Seebeck
+measurements on a thermocouple connected to the ferromagnet. The observed
+resonance peak shape is in agreement with the Landau-Lifshitz-Gilbert equation
+and is compared with thermoelectric finite element modeling. Unlike other
+methods, this technique is not restricted to electrically conductive media and
+is therefore also applicable to for instance ferromagnetic insulators.",1108.1286v1
+2011-08-30,Spin Wave Diffraction and Perfect Imaging of a Grating,"We study the diffraction of Damon-Eshbach-type spin waves incident on a
+one-dimensional grating realized by micro slits in a thin permalloy film. By
+means of time-resolved scanning Kerr microscopy we observe unique diffraction
+patterns behind the grating which exhibit replications of the spin-wave field
+at the slits. We show that these spin-wave images, with details finer than the
+wavelength of the incident Damon-Eshbach spin wavelength, arise from the
+strongly anisotropic spin wave dispersion.",1108.5883v1
+2012-02-29,Spin wave modes in magnetic nanodisks under in-plane magnetic field,"The size dependence of spin wave modes in a circular Permalloy (Py) nanodisk
+under an in-plane magnetic field is systematically studied by using
+micromagnetics simulations. We show that as the disk diameter is increased, the
+resonance frequency of the backward mode deceases while that of the uniform
+mode increases. The avoided crossing of resonance frequencies of the uniform
+mode and the backward mode appears in the plot of the size dependence of
+resonance frequencies and the backward mode turns into the so-called ""edge
+mode"" for large nanodisks.",1202.6464v1
+2012-03-28,Charge Imbalance and Crossed Andreev reflection in Py/Ta Devices,"Crossed Andreev reflection in a lateral spin valve geometry device is an
+aspect of considerable recent interest, particularly with regards to Cooper
+pair splitting experiments to realize solid state quantum entanglement. In this
+work, devices are fabricated consisting of two ferromagnetic permalloy (Py)
+electrodes contacted by a overlaid perpendicular superconducting Ta electrode,
+of variable lateral in-plane offset within the expected BCS superconducting
+coherence length $\xi_0$. Experimental electrical transport measurements are
+presented of local and nonlocal conduction, showing characteristics of
+non-local or crossed Andreev reflection in the superconducting state at low
+temperatures in addition to nonlocal effects divergent for T$\rightarrow$T$_c$
+attributed to nonlocal charge imbalance.",1203.6296v1
+2012-04-05,The influence of individual lattice defects on the domain structure in magnetic antidot lattices,"We numerically and experimentally investigate the influence of single defects
+consisting of a missing antidot on the spin configurations in rectangular
+permalloy antidot lattices. The introduction of such lattice defects leads to
+the nucleation of complex domain structures after the decay of a saturating
+magnetic field. Micromagnetic simulations yield four typical domain
+configurations around the defect having distinct energy densities. The
+existence of the four spin configurations is confirmed by magnetic force
+microscopy on antidot lattices containing individual defects.",1204.1183v2
+2012-05-25,Spin wave amplification driven by heat flow: the role of damping and exchange interaction,"In this article we report on micromagnetic simulations performed on a
+permalloy nanostructure in presence of a uniform thermal gradient. Our
+numerical simulations show that heat flow is an effective mean to compensate
+the damping, and that the gradients at which spin-wave amplification is
+observed are experimentally accessible. In particular, we have studied the role
+of the Gilbert damping parameter on spin-wave amplification.",1205.5650v2
+2012-07-19,Anatomy of Demagnetizing and Exchange Fields in Magnetic Nanodots Influenced by 3D Shape Modifications,"Hysteresis loops of 3D ferromagnetic permalloy nano-half-balls (dots) with
+100 nm base diameter have been examined by means of LLG micromagnetic
+simulations and finite element methods. Tests were carried out with two
+orthogonal directions of the externally applied field at 10 kA/(m.ns) field
+sweeping speed. The comparison of samples with different 3D modifications at
+the sub-10nm scale, accessible by nowadays lithographic techniques, enables
+conclusions about different mechanisms of competition between demagnetizing and
+exchange fields. Design paradigms provided here can find possible applications
+in magneto-electronic devices.",1207.4673v1
+2013-01-28,Pinning of a Bloch point by an atomic lattice,"Bloch points are magnetic topological defects. The discrete nature of a
+magnetic lattice creates a periodic potential that can pin a Bloch point. The
+pinning force is of the order of the exchange constant, a few piconewtons in a
+typical ferromagnet (permalloy). A domain wall containing a Bloch point can
+have a sizable depinning field in the tens of oersted.",1301.6452v2
+2013-03-30,Features of amplification of dipole magnetic field with linear ferromagnetic concentrator,"Amplification of a low frequency magnetic field from a dipole source by means
+of linear ferromagnetic concentrator of different dimensions (permalloy micro
+wire) has been investigated experimentally. The results obtained strengthen the
+validity of the analytical relation for amplification which allows for
+nonlinear dependence of the magnetic permeability upon the value and
+distribution of the dipole field over concentrator length.",1304.0111v1
+2013-06-05,Equilibrium states of soft magnetic hemispherical shell,"The ground state of hemispherical permalloy magnetic shell is studied. There
+exist two magnetic phases: the onion state and the vortex one. The phase
+diagram is systematically analyzed in a wide range of geometrical parameters.
+Possible transitions between different phases are analyzed using the
+combination of analytical calculations and micromagnetic simulations.",1306.1249v2
+2013-09-29,Magnetic shield of PMT used in DAMPE electromagnetic calorimeter,"The magnetic characteristics of photomultiplier tube R5610A-01 are studied in
+this paper. The experimental data shows that the gain of R5610A-01 loses about
+53% when the magnetic field is 3G along its +X axis. A cylinder of one-layer
+permalloy strip is able to reduce the effect of 3G magnetic field on the PMT's
+gain to less than 1%.",1309.7638v4
+2013-10-23,Magnetization Characteristic of Ferromagnetic Thin Strip by Measuring Anisotropic Magnetoresistance and Ferromagnetic Resonance,"The magnetization characteristic in a permalloy thin strip is investigated by
+electrically measuring the anisotropic magnetoresistance and ferromagnetic
+resonance in in-plane and out-of-plane configurations. Our results indicate
+that the magnetization vector can rotate in the film plane as well as out of
+the film plane by changing the intensity of external magnetic field of certain
+direction. The magnetization characteristic can be explained by considering
+demagnetization and magnetic anisotropy. Our method can be used to obtain the
+demagnetization factor, saturated magnetic moment and the magnetic anisotropy.",1310.6117v1
+2014-02-11,Fundamental energy limits in the physics of small-scale binary switches,"Binary switches are the basic element of modern digital computers. In this
+paper we discuss the role of switching procedure with reference to the
+fundamental limits in minimum energy dissipation. We show that the minimum
+energy depends on the switching procedure and test this result with
+micromagnetic simulations of a nanoscale switch realized with single
+cylindrical element of permalloy (NiFe). Finally we establish a relation
+between minimum energy and switching error probability.",1403.1800v1
+2014-07-21,Josephson junction with a magnetic vortex,"We have studied Josephson tunneling through a circularly polarized micron or
+submicron-size disk of a soft ferromagnetic material. Such a disk contains a
+vortex that exhibits rich classical dynamics and has recently been proposed as
+a tool to study quantum dynamics of the nanoscale vortex core. The change in
+the Josephson current that is related to a tiny displacement of the vortex core
+has been computed analytically and plotted numerically for permalloy disks used
+in experiments. It is shown that a Josephson junction with a magnetic disk in
+the vortex state can be an interesting physical system that may be used to
+measure the nanoscale motion of the magnetic vortex.",1407.5419v1
+2014-07-29,Faceting Oscillations in Nano-Ferroelectrics,"We observe periodic faceting of 8-nm diameter ferroelectric disks on a 10 s
+time-scale when thin Pb(Zr0.52Ti0.48)O3 (PZT) film is exposed to constant
+high-resolution transmission electron microscopy (HRTEM) beams. The oscillation
+is between circular disk geometry and sharply faceted hexagons. The behavior is
+analogous to that of spin structure and magnetic domain wall velocity
+oscillations in permalloy [A. Bisig et al., Nature Commun. 4, 2328 (2013)],
+involving overshoot and de-pinning from defects [C. P. Amann, et al., J. Rheol.
+57, 149-175 (2013)].",1407.7646v1
+2015-04-22,Fork stamping of pristine carbon nanotubes onto ferromagnetic contacts for spin-valve devices,"We present a fabrication scheme called 'fork stamping' optimized for the dry
+transfer of individual pristine carbon nanotubes (CNTs) onto ferromagnetic
+contact electrodes fabricated by standard lithography. We demonstrate the
+detailed recipes for a residue-free device fabrication and in-situ current
+annealing on suspended CNT spin-valve devices with ferromagnetic Permalloy (Py)
+contacts and report preliminary transport characterization and
+magnetoresistance experiments at cryogenic temperatures. This scheme can
+directly be used to implement more complex device structures, including
+multiple gates or superconducting contacts.",1504.05693v1
+2015-10-25,Dependence of transverse magneto-thermoelectric effects on inhomogeneous magnetic fields,"Transverse magneto-thermoelectric effects are studied in permalloy thin films
+grown on MgO substrates. We find that small parasitic magnetic fields below 1
+Oe can produce artifacts of the order of 1 % of the amplitude of the
+anisotropic magneto-thermopower which is also detected in the experiments. The
+measured artifacts reveal a new source of uncertainties for the detection of
+the transverse spin Seebeck effect. Taking these results into account we
+conclude that the contribution of the transverse spin Seebeck effect to the
+detected voltages is below the noise level of 20 nV.",1510.07241v1
+2016-01-17,Experimental observation of spin to charge current conversion at non-magnetic metal/Bi2O3 interfaces,"We here demonstrate the interfacial spin to charge current conversion by
+means of spin pumping from a ferromagnetic Permalloy (Py: Ni80Fe20) to a
+Cu/Bi2O3 interface. A clear signature of the spin to charge current conversion
+was observed in voltage spectrum of a Py/Cu/Bi2O3 trilayer film whereas no
+signature in a Py/Cu and Py/Bi2O3 bilayer films. We also found that the
+conversion coefficient strongly depended on Cu thickness, reflecting the
+thickness dependent momentum relaxation time in Cu layer.",1601.04292v1
+2016-02-22,Exchange magnon induced resistance asymmetry in permalloy spin-Hall oscillators,"We investigate magnetization dynamics in a spin-Hall oscillator using a
+direct current measurement as well as conventional microwave spectrum analysis.
+When the current applies an anti-damping spin-transfer torque, we observe a
+change in resistance which we ascribe to the excitation of incoherent exchange
+magnons. A simple model is developed based on the reduction of the effective
+saturation magnetization, quantitatively explaining the data. The observed
+phenomena highlight the importance of exchange magnons on the operation of
+spin-Hall oscillators.",1602.06710v1
+2016-10-19,Resonant Magnetization Switching Conditions of an Exchange-coupled Bilayer under Spin Wave Excitation,"We systematically investigated the spin wave-assisted magnetization switching
+(SWAS) of a L10-FePt / Ni81Fe19 (Permalloy; Py) exchange-coupled bilayer using
+a pulse-like rf field (hrf) and mapped the switching events in the magnetic
+field (H) - hrf frequency (f) plane to reveal the switching conditions. The
+switching occurred only in a limited region following the dispersion
+relationship of the perpendicular standing spin wave (PSSW) modes in Py. The
+results indicate that SWAS is a resonant magnetization switching process, which
+is different from the conventional microwave assisted switching, and has the
+potential to be applied to selective switching for multilevel recording media.",1610.05864v1
+2017-01-06,Imaging magnetic vortex configurations in ferromagnetic nanotubes,"We image the remnant magnetization configurations of CoFeB and permalloy
+nanotubes (NTs) using x-ray magnetic circular dichroism photo-emission electron
+microscopy. The images provide direct evidence for flux-closure configurations,
+including a global vortex state, in which magnetization points
+circumferentially around the NT axis. Furthermore, micromagnetic simulations
+predict and measurements confirm that vortex states can be programmed as the
+equilibrium remnant magnetization configurations by reducing the NT aspect
+ratio.",1701.01685v1
+2018-06-18,Relation between unidirectional spin Hall magnetoresistance and spin current-driven magnon generation,"We perform electronic measurements of unidirectional spin Hall
+magnetoresistance (USMR) in a Permalloy/Pt bilayer, in conjunction with
+magneto-optical Brillouin light spectroscopy of spin current-driven magnon
+population. We show that the current dependence of USMR closely follows the
+dipolar magnon density, and that both dependencies exhibit the same scaling
+over a large temperature range of 80-400 K. These findings demonstrate a close
+relationship between spin current-driven magnon generation and USMR, and
+indicate that the latter is likely dominated by the dipolar magnons.",1806.06581v1
+2014-06-23,Fast minute magnetic field coil for time-resolved nanospintronics,"Nanospintronic and related research often requires the application of fast
+rising magnetic field pulses in the plane of the studied planar structure. We
+have designed and fabricated sub-milimeter-sized coils capable of delivering
+pulses of the magnetic field up to ~ 500 Oe in the plane of the sample with the
+rise time of order of 10 ns. The placement of the sample above the coil allows
+for an easy access to its surface with manipulators or light beams for, e.g.,
+Kerr microscopy. We use the fabricated coil to drive magnetic domain walls in 1
+${\mu}$ m wide permalloy wires and measure magnetic domain wall velocity as a
+function of the applied magnetic field.",1406.5901v1
+2018-12-26,Probing the Relationship between Anisotropic Magnetoresistance and Magnetization of ferromagnetic films,"The anisotropic magnetoresistance (AMR) in thin permalloy strips was
+calculated at each steps during magnetization by the finite element method. The
+magnetization at equilibrium under different external fields was obtained by
+micromagnetic simulations, while the resistance with different magnetization
+was obtained by solving the Poisson equations iteratively until
+self-consistence. We find that the relation between magnetization and AMR
+deviates from the Stoner-Wohlfarth prediction when the magnetization is reduced
+from saturation. The reason is that the demagnetization is not necessarily from
+coherent rotation of the magnetic moment. We conclude that it is necessary to
+use numeric simulations to optimize the responses of AMR sensors.",1812.10294v1
+2020-05-11,Chiral Walker breakdown in the U-shaped Permalloy nanotube,"The motion of transverse domain walls (DWs) in U-shaped ferromagnetic
+nanotube which owns two different geometric confinements were investigated by
+micromagnetic simulation. Driven by unidirectional magnetic fields, the
+chirality-dependent DW structure and velocity under low fields and two phases
+of chiral Walker breakdown processes under high fields were observable,
+respectively. All these chirality-dependent behaviors can be attributed to the
+different dynamics of magnetizations in geometric confinements. Additionally,
+DW structures have different responses and sensitivity to applied fields,
+leading to a hierarchy and complex Walker breakdown processes. This supplies a
+new perspective for manipulating DW chirality.",2005.05162v2
+2016-03-23,"Nucleation, imaging and motion of magnetic domain walls in cylindrical nanowires","We report several procedures for the robust nucleation of magnetic domain
+walls in cylindrical permalloy nanowires. Specific features of the magnetic
+force microscopy contrast of such soft wires are discussed, with a view to
+avoid the misinterpretation of the magnetization states. The domain walls could
+be moved under quasistatic magnetic fields in the range 0.1--10 mT.",1603.07240v1
+2016-12-16,Relaxation mechanism driven by spin angular momentum absorption throughout antiferromagnetic phase transition in NiFe surface oxides,"We report an alternative mechanism for the physical origin of the
+temperature-dependent ferromagnetic relaxation of Permalloy (NiFe) thin films.
+Through spin-pumping experiments, we demonstrate that the peak in the
+temperature-dependence of NiFe damping can be understood in terms of enhanced
+spin angular momentum absorption at the magnetic phase transition in
+antiferromagnetic surface-oxidized layers. These results suggest new avenues
+for the investigation of an incompletely-understood phenomenon in physics.",1612.05556v1
+2019-08-21,Artificial Spin Ice Phase-Change Memory Resistors,"We study the implications of the anisotropic magnetic resistance on permalloy
+nanowires, and in particular on the property of the resistance depending on the
+type of lattice. We discuss how the internal spin configuration of artificial
+spin ice nanowires can affect their effective resistive state, and which
+mechanisms can introduce a current-dependent effect dynamic resistive state. We
+discuss a spin-induced thermal phase-change mechanism, and an athermal
+domain-wall spin inversion. In both cases we observe memory behavior
+reminiscent of a memristor, with an I-V hysteretic pinched behavior.",1908.08073v1
+2021-09-17,Fabricacion de un magnetron sputtering para deposito de peliculas nanometricas magneticas,"This paper presents the development of scientific instrumentation for the
+fabrication of ferromagnetic thin films, by sputtering technique, for the use
+of 2-inch-diameter targets. Thin films were deposited using Permalloy alloy
+(Ni80Fe20) as ferromagnetic material at room temperature on Si (001)
+substrates. The film thicknesses were measured with profilometry and a
+deposition rate for this alloy of 16.2 nm/min was calculated. Scanning electron
+microscopy showed a continuous film formation and a chemical composition
+similar to the target",2109.08649v1
+2022-11-04,Observation of Spin Current Hermiticity,"The spin Hall effect is one of the most relevant effects in spintronics and
+the key to conversion from charge current into spin current. We report here a
+phenomenon, which appears in response to the spin Hall effect and represents
+the anti-polarization of the spin current due to the coupling between
+interfacial magnetic anisotropies. Such an effect produces a Hermitian spin
+current. We realized experiments on permalloy (Py) and Cobalt (Co) bilayers to
+discuss this phenomenon.",2211.02334v1
+2023-06-05,Observation of anisotropic magneto-inductance effect,"We have discovered a new phenomenon that inductance oscillates as a function
+of the angle between an in-plane magnetic field and an electric current
+direction in permalloy films, which we have named ""the anisotropic
+magneto-inductance (AML) effect"". We have investigated the dependences of the
+AML effect on the size and voltage. The length, frequency, and amplitude
+dependences suggest that the AML effect should be evaluated in terms of
+""inductivity"". Inductors based on this AML effect have the potential to be
+variable, on-chip, and one billion times smaller than the small commercial
+inductor.",2306.02757v1
+2024-03-11,Magnetic vortex polarity reversal induced gyrotropic motion spectrum splitting in a ferromagnetic disk,"We investigate the gyrotropic motion of the magnetic vortex core in a chain
+of a few micron-sized Permalloy disks by electrical resistance measurement with
+amplitude-modulated magnetic field. We observe a distinctive splitting of the
+resistance peak due to the resonant vortex-core motion under heightened radio
+frequency (RF) magnetic field excitation. Our micromagnetic simulation
+identifies the splitting of the resonant peak as an outcome of vortex polarity
+reversal under substantial RF amplitudes. This study enhances our understanding
+of nonlinear magnetic vortex dynamics amidst large RF amplitudes and proposes a
+potential pathway for spintronic neural computing thanks to their unique and
+controllable magnetization dynamics.",2403.06491v1
+2024-03-21,Efecto Hall de espin inverso en peliculas de Nb Mo y Bi por bombeo de espin,"The inverse spin Hall effect used for detection of spin currents was observed
+by voltage measurements in bilayers of normal metal (NM)/ferromagnetic metal
+(FM), using Nb, Mo and Bi as normal metal and Permalloy (Py,
+Ni$_{81}$Fe$_{19}$) as ferromagnetic metal. The spin current was generated by
+the spin pumping effect with ferromagnetic resonance. The samples were
+deposited by dc magnetron sputtering at room temperature on Si (001)
+substrates. The three bilayers of Nb/Py, Mo/Py and Bi/Py had a spin-orbit
+coupling large enough to observe the voltage generation by spin Hall effect",2403.17976v1
+2004-07-14,An ab-initio theoretical investigation of the soft-magnetic properties of permalloys,"We study Ni80Fe20-based permalloys with the relativistic spin-polarized
+Korringa-Kohn-Rostoker electronic structure method. Treating the compositional
+disorder with the coherent potential approximation, we investigate how the
+magnetocrystalline anisotropy, K, and magnetostriction, lambda, of Ni-rich
+Ni-Fe alloys vary with the addition of small amounts of non-magnetic transition
+metals, Cu and Mo. From our calculations we follow the trends in K and lambda
+and find the compositions of Ni-Fe-Cu and Ni-Fe-Mo where both are near zero.
+These high permeability compositions of Ni-Fe-Cu and Ni-Fe-Mo match well with
+those discovered experimentally. We monitor the connection of the magnetic
+anisotropy with the number of minority spin electrons, Nmin. By raising Nmin
+via artificially increasing the band-filling of Ni80Fe20, we are able to
+reproduce the key features that underpin the magnetic softening we find in the
+ternary alloys. The effect of band-filling on the dependence of
+magnetocrystalline anisotropy on atomic short-range order in Ni80Fe20 is also
+studied. Our calculations, based on a static concentration wave theory,
+indicate that the susceptibility of the high permeability of the Ni-Fe-Cu and
+Ni-Fe-Mo alloys to their annealing conditions is also strongly dependent on the
+alloys' compositions. An ideal soft magnet appears from these calculations.",0407355v1
+2009-05-12,Magnetotransport effects of ultrathin Ni80Fe20 films probed in-situ,"We have investigated the magnetoresistance of Permalloy (Ni80Fe20) films with
+thicknesses ranging from a single monolayer to 12 nm, grown on Al2O3, MgO and
+SiO2 substrates. Growth and transport measurements were carried out under
+cryogenic conditions in UHV. Applying in-plane magnetic vector fields up to 100
+mT, the magnetotransport properties are ascertained during growth. With
+increasing thickness the films exhibit a gradual transition from tunneling
+magnetoresistance to anisotropic magnetoresistance. This corresponds to the
+evolution of the film structure from separated small islands to a network of
+interconnected grains as well as the transition from superparamagnetic to
+ferromagnetic behavior of the film. Using an analysis based on a theoretical
+model of the island growth, we find that the observed evolution of the
+magnetoresistance in the tunneling regime originates from the changes in the
+island size distribution during growth. Depending on the substrate material,
+significant differences in the magnetoresistance response in the transition
+regime between tunneling magnetoresistance and anisotropic magnetoresistance
+were found. We attribute this to an increasingly pronounced island growth and
+slower percolation process of Permalloy when comparing growth on SiO2, MgO and
+Al2O3 substrates. The different growth characteristics result in a markedly
+earlier onset of both tunneling magnetoresistance and anisotropic
+magnetoresistance for SiO2. For Al2O3 in particular the growth mode results in
+a structure of the film containing two different contributions to the
+ferromagnetism which lead to two distinct coercive fields in the high thickness
+regime.",0905.1819v2
+2011-07-28,Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano-pillar,"We report on a spectroscopic study of the spin-wave eigen-modes inside an
+individual normally magnetized two layers circular nano-pillar
+(Permalloy$|$Copper$|$Permalloy) by means of a Magnetic Resonance Force
+Microscope (MRFM). We demonstrate that the observed spin-wave spectrum
+critically depends on the method of excitation. While the spatially uniform
+radio-frequency (RF) magnetic field excites only the axially symmetric modes
+having azimuthal index $\ell=0$, the RF current flowing through the
+nano-pillar, creating a circular RF Oersted field, excites only the modes
+having azimuthal index $\ell=+1$. Breaking the axial symmetry of the
+nano-pillar, either by tilting the bias magnetic field or by making the pillar
+shape elliptical, mixes different $\ell$-index symmetries, which can be excited
+simultaneously by the RF current. Experimental spectra are compared to
+theoretical prediction using both analytical and numerical calculations. An
+analysis of the influence of the static and dynamic dipolar coupling between
+the nano-pillar magnetic layers on the mode spectrum is performed.",1107.5699v2
+2013-01-16,Self-induced inverse spin Hall effect in permalloy at room temperature,"Inverse spin Hall effect (ISHE) allows the conversion of pure spin current
+into charge current in nonmagnetic materials (NM) due to spin-orbit interaction
+(SOI). In ferromagnetic materials (FM), SOI is known to contribute to anomalous
+Hall effect (AHE), anisotropic magnetoresistance (AMR), and other
+spin-dependent transport phenomena. However, SOI in FM has been ignored in ISHE
+studies in spintronic devices, and the possibility of ""self-induced ISHE"" in FM
+has never been explored until now. In this paper, we demonstrate the
+experimental verification of ISHE in FM. We found that the spin-pumping-induced
+spin current in permalloy (Py) film generates a transverse electromotive force
+(EMF) in the film itself, which results from the coupling of spin current and
+SOI in Py. The control experiments ruled out spin rectification effect and
+anomalous Nernst effect as the origin of the EMF.",1301.3580v5
+2014-10-21,Neutron Reflectometry Studies on Magnetic Stripe Domains in Permalloy/Superconductor bilayers,"We explored changes in magnetic domain structures in a magnetic layer due to
+the onset of the superconductivity of an adjacent superconductive layer using
+neutron reflectometry. Magnetic domain structures in 1~$\mu$m thick permalloy
+(Py) films were studied as functions of magnetic field, temperature and under
+the influence of the onset of superconductivity in a neighboring layer. Bragg
+peaks in the off-specular scattering were observed at low fields following
+saturation with an in-plane field, which are attributed to the quasi-parallel
+magnetic stripes along the field direction. During the magnetization reversal
+from saturation, the stripe pattern shows increases in the period, the
+transverse coherence length (\textit{i.e.}, perpendicular to the stripes) and
+the amplitude of the out-of-plane magnetization component. The coherence length
+of the magnetic stripes is anisotropic in the remnant state with the
+longitudinal coherence length (\textit{i.e.}, along the stripes) being larger
+than the transverse one. The stripe period shows a weak temperature dependence
+between 300~K and 3~K, but no abrupt change in the period is observed when the
+temperature crosses the superconducting critical temperature.",1410.5520v1
+2015-04-29,Role of transparency of platinum-ferromagnet interface in determining intrinsic magnitude of spin Hall effect,"The spin Hall effect (SHE) converts charge current to pure spin currents in
+orthogonal directions in materials that have significant spin-orbit
+coupling.The efficiency of the conversion is described by the spin Hall Angle
+(SHA). The SHA can most readily be inferred by using the generated spin
+currents to excite or rotate the magnetization of ferromagnetic films or
+nano-elements via spin-transfer torques.Some of the largest spin torque derived
+spin Hall angles (ST-SHA) have been reported in platinum. Here we show, using
+spin torque ferromagnetic resonance (ST-FMR) measurements, that the
+transparency of the Pt-ferromagnet interface to the spin current plays a
+central role in determining the magnitude of the ST-SHA. We measure a much
+larger ST-SHA in Pt/cobalt (~0.11) compared to Pt/permalloy (~0.05) bilayers
+when the interfaces are assumed to be completely transparent. Taking into
+account the transparency of these interfaces, as derived from spin-mixing
+conductances, we find that the intrinsic SHA in platinum has a much higher
+value of 0.19 +- 0.04 as compared to the ST-SHA. The importance of the
+interface transparency is further exemplified by the insertion of atomically
+thin magnetic layers at the Pt/permalloy interface that we show strongly
+modulates the magnitude of the ST-SHA.",1504.07929v1
+2015-12-01,Magnetization reversal of an individual exchange biased permalloy nanotube,"We investigate the magnetization reversal mechanism in an individual
+permalloy (Py) nanotube (NT) using a hybrid magnetometer consisting of a
+nanometer-scale SQUID (nanoSQUID) and a cantilever torque sensor. The Py NT is
+affixed to the tip of a Si cantilever and positioned in order to optimally
+couple its stray flux into a Nb nanoSQUID. We are thus able to measure both the
+NT's volume magnetization by dynamic cantilever magnetometry and its stray flux
+using the nanoSQUID. We observe a training effect and temperature dependence in
+the magnetic hysteresis, suggesting an exchange bias. We find a low blocking
+temperature $T_B = 18 \pm 2$ K, indicating the presence of a thin
+antiferromagnetic native oxide, as confirmed by X-ray absorption spectroscopy
+on similar samples. Furthermore, we measure changes in the shape of the
+magnetic hysteresis as a function of temperature and increased training. These
+observations show that the presence of a thin exchange-coupled native oxide
+modifies the magnetization reversal process at low temperatures. Complementary
+information obtained via cantilever and nanoSQUID magnetometry allows us to
+conclude that, in the absence of exchange coupling, this reversal process is
+nucleated at the NT's ends and propagates along its length as predicted by
+theory.",1512.00199v1
+2016-02-01,Facet-dependent giant spin orbit torque in single crystalline antiferromagnetic Ir-Mn / ferromagnetic permalloy bilayers,"There has been considerable interest in spin-orbit torques for the purpose of
+manipulating the magnetization of ferromagnetic (FM) films or nano-elements for
+spintronic technologies. Spin-orbit torques are derived from spin currents
+created from charge currents in materials with significant spin-orbit coupling
+that diffuse into an adjacent FM material. There have been intensive efforts to
+search for candidate materials that exhibit large spin Hall angles, i.e.
+efficient charge to spin current conversion. Here we report, using spin torque
+ferromagnetic resonance, the observation of a giant spin Hall angle of up to
+~0.35 in (100) oriented single crystalline antiferromagnetic (AF) IrMn3 thin
+films, coupled to ferromagnetic permalloy layers, and a spin Hall angle that is
+about three times smaller in (111) oriented films. For the (100) oriented
+samples we show that the magnitude of the spin Hall angle can be significantly
+changed by manipulating the populations of the various AF domains through field
+annealing. Using ab-initio calculations we show that the triangular AF
+structure of IrMn3 gives rise to a substantial intrinsic spin Hall conductivity
+that is three times larger for the (100) than for the (111) orientations,
+consistent with our experimental findings.",1602.00670v1
+2016-02-19,A systematic study of magnetodynamic properties at finite temperatures in doped permalloy from first principles calculations,"By means of first principles calculations, we have systematically
+investigated how the magnetodynamic properties Gilbert damping, magnetization
+and exchange stiffness are affected when permalloy (Py)
+(Fe$_{0.19}$Ni$_{0.81}$) is doped with 4d or 5d transition metal impurities. We
+find that the trends in the Gilbert damping can be understood from relatively
+few basic parameters such as the density of states at the Fermi level, the
+spin-orbit coupling and the impurity concentration. % The temperature
+dependence of the Gilbert damping is found to be very weak which we relate to
+the lack of intraband transitions in alloys. % Doping with $4d$ elements has no
+major impact on the studied Gilbert damping, apart from diluting the host.
+However, the $5d$ elements have a profound effect on the damping and allows it
+to be tuned over a large interval while maintaining the magnetization and
+exchange stiffness. % As regards spin stiffness, doping with early transition
+metals results in considerable softening, whereas late transition metals have a
+minor impact. % Our result agree well with earlier calculations where
+available. In comparison to experiments, the computed Gilbert damping appears
+slightly underestimated while the spin stiffness show good general agreement.",1602.06201v2
+2018-03-23,Observation of hedgehog skyrmions in sub-100 nm soft magnetic nanodots,"Magnetic skyrmions are nanometric spin textures of outstanding potential for
+spintronic applications due to unique features governed by their non-trivial
+topology. It is well known that skyrmions of definite chirality are stabilized
+by the Dzyaloshinskii-Moriya exchange interaction (DMI) in bulk
+non-centrosimmetric materials or ultrathin films with strong spin-orbit
+coupling in the interface. In this work, we report on the detection of magnetic
+hedgehog-skyrmions at room temperature in confined systems with neither DMI nor
+perpendicular magnetic anisotropy. We show that soft magnetic (permalloy)
+nanodots are able to host non- chiral hedgehog skyrmions that can be further
+stabilized by the magnetic field arising from the Magnetic Force Microscopy
+probe. Analytical calculations and micromagnetic simulations confirmed the
+existence of metastable N\'eel skyrmions in permalloy nanodots even without
+external stimuli in a certain size range. Our work implies the existence of a
+new degree of freedom to create and manipulate skyrmions in soft nanodots. The
+stabilization of skyrmions in soft magnetic materials opens a possibility to
+study the skymion magnetization dynamics otherwise limited due to the large
+damping constant coming from the high spin-orbit coupling in materials with
+high magnetic anisotropy.",1803.08768v1
+2021-07-05,Inverse magnetic hysteresis of the Josephson supercurrent: study of the magnetic properties of thin niobium/permalloy (Fe_{20}Ni_{80}) interfaces,"We propose a picture for the magnetic properties of
+superconductor/ferromagnet (S/F) heterostructures based on Nb and permalloy
+(Py: Fe_{20}Ni_{80}). By measuring the magnetic moment as a function of the
+temperature in S/F/S trilayers for different thicknesses of the middle F layer,
+we give evidence of the presence of a magnetic stray field of the F layer. For
+values of F-layer thickness below a threshold, we establish a correlation
+between the magnetic measurements of the S/F/S trilayers and the anomalous
+magnetic dependence of the critical current in S/insulator/thin superconducting
+film/F/S (SIsFS) Josephson junctions (JJs). These complementary investigations
+provide a self-consistent method to fully characterize S/F heterostructures and
+possibly demonstrate effects arising from the mutual interactions between
+ferromagnetism and superconductivity. A shift in the Fraunhofer critical
+current oscillations has been observed in the opposite direction to the one
+commonly observed in JJs with F barriers, as it has been recently predicted by
+inverse and electromagnetic proximity theories. This inverse memory effect is
+relevant for the design of these heterostructures as memory cells and
+spintronic devices.",2107.02142v1
+2019-01-26,Effects of Nanodots Shape and Lattice Constants on the Spin Wave Dynamics of Patterned Permalloy Dots,"Micromagnetic simulations studies on Permalloy (Ni80Fe20) nanodot with
+different shape and edge-to-edge separation (s) down to 25nm arranged in square
+lattice are reported. We observe the significant variation of spin-wave (SW)
+dynamics of nanodots of different shapes (triangular, diamond and hexagon) and
+of fixed dot diameter 100nm with varying s. Modes for single dot are
+transformed in an array into multiple quantized, edge and centre modes for
+different shapes and edge-to-edge separations, with different spin wave
+frequencies and peak intensities. Specifically, in the triangular dot sample, a
+broad range of mode frequencies is observed with highest SW frequency 14.7 GHz.
+For separation less than 100nm, the SW frequencies undergoes significant
+modification due to the varying nature of the magnetostatic and dipolar
+interaction in the array while for separation above 100nm, the SW frequency
+mostly remain constant. The power profiles confirm the nature of the observed
+modes. The spatial profiles of magnetostatic field are determined by a
+combination of internal magnetic-field profiles within the nanodots and the
+magnetostatic fields within the lattice. The inter-dots interaction of
+magnetostatic field shows dipolar and quadrupole contributions for all the
+shapes. Interestingly, vortex states with shifted core and polarity are
+observed in the array for all the shapes at Hbias = 0. Our results provide
+important understanding about the tunability of SW spectra in the array of
+triangular, diamond and hexagon shaped nanoelements.",1901.09155v1
+2019-07-03,Chiral asymmetry detected in a 2D array of permalloy square nanomagnets using circularly polarized X ray Resonant Magnetic Scattering,"The sensitivity of Circularly polarized X ray Resonant Magnetic Scattering
+(CXRMS) to chiral asymmetry has been demonstrated. The study was performed on a
+2D array of Permalloy (Py) square nanomagnets of 700 nm lateral size arranged
+in a chess lattice of 1000 nm lattice parameter. Previous X ray Magnetic
+Circular Dichroism Photoemission Electron microscopy (XMCD-PEEM) images on this
+sample showed the formation of vortices at remanence and a preference in their
+chiral state. The magnetic hysteresis loops of the array along the diagonal
+axis of the squares indicate a non-negligible and anisotropic interaction
+between vortices. The intensity of the magnetic scattering using circularly
+polarized light along one of the diagonal axes of the square magnets becomes
+asymmetric in intensity in the direction transversal to the incident plane at
+fields where the vortex states are formed. The asymmetry sign is inverted when
+the direction of the applied magnetic field is inverted. The result is the
+expected in the presence of an unbalanced chiral distribution. The effect is
+observed by CXRMS due to the interference between the charge scattering and the
+magnetic scattering.",1907.02016v2
+2019-02-21,Effects of the removal of Ta capping layer on the magnetization dynamics of Permalloy thin films,"We have investigated the spin wave dynamics of Permalloy (Py) thin films with
+and without a Ta capping layer for varying Py thickness (15 nm, 20 nm and 30
+nm) using all optical time-resolved magneto-optical Kerr effect measurements.
+XPS measurements confirm the oxidation of the originally-prepared samples and
+also that the removal of the Ta capping layer is achievable by a few sputtering
+cycles. The magnetic field strength dependencies of the spin wave modes with
+the variation of the Py film thickness for the samples are studied. We observe
+that the presence of the Ta capping layer reduces the precessional frequencies
+of the samples while the samples without a Ta capping layer enhance the role of
+Py thickness. We also observe that the decay time of spin waves is highly
+dependent on the top layer of the samples. The decay time increases with
+increasing Py thicknesses for Ta/Py/Ta samples implying that the enhancement of
+decay time is caused by the Ta/Py/Ta interfaces. Whereas, for Ta/Py samples the
+decay time decreases with increasing Py thickness. The results of this work
+extend the knowledge on the magnetization dynamics of Py thin films giving
+information on how to resume and even enhance the spin mobility after a
+deleterious oxidation process. This can open new scenarios on the building
+process and on the maintenance of fast magnetic switching devices.",1902.07832v1
+2019-06-03,Layer-dependent spin-orbit torques generated by the centrosymmetric transition metal dichalcogenide $β$-MoTe$_2$,"Single-crystal materials with sufficiently low crystal symmetry and strong
+spin-orbit interactions can be used to generate novel forms of spin-orbit
+torques on adjacent ferromagnets, such as the out-of-plane antidamping torque
+previously observed in WTe$_2$/ferromagnet heterostructures. Here, we present
+measurements of spin-orbit torques produced by the low-symmetry material
+$\beta$-MoTe$_2$, which unlike WTe$_2$ retains bulk inversion symmetry. We
+measure spin-orbit torques on $\beta$-MoTe$_2$/Permalloy heterostructures using
+spin-torque ferromagnetic resonance as a function of crystallographic alignment
+and MoTe$_2$ thickness down to the monolayer limit. We observe an out-of-plane
+antidamping torque with a spin torque conductivity as strong as 1/3 of that of
+WTe$_2$, demonstrating that the breaking of bulk inversion symmetry in the
+spin-generation material is not a necessary requirement for producing an
+out-of-plane antidamping torque. We also measure an unexpected dependence on
+the thickness of the $\beta$-MoTe$_2$ -- the out-of-plane antidamping torque is
+present in MoTe$_2$/Permalloy heterostructures when the $\beta$-MoTe$_2$ is a
+monolayer or trilayer thick, but goes to zero for devices with bilayer
+$\beta$-MoTe$_2$.",1906.01068v1
+2017-10-19,Spin-triplet supercurrent in Josephson junctions containing a synthetic antiferromagnet with perpendicular magnetic anisotropy,"We present measurements of Josephson junctions containing three magnetic
+layers with noncolinear magnetizations. The junctions are of the form
+$S/F^{\prime}/N/F/N/F^{\prime \prime}/S$, where $S$ is superconducting Nb,
+$F^\prime$ is either a thin Ni or Permalloy layer with in-plane magnetization,
+$N$ is the normal metal Cu, $F$ is a synthetic antiferromagnet (SAF) with
+magnetization perpendicular to the plane, composed of Pd/Co multilayers on
+either side of a thin Ru spacer, and $F^{\prime \prime}$ is a thin Ni layer
+with in-plane magnetization. The supercurrent in these junctions decays more
+slowly as a function of the $F$-layer thickness than for similar spin-singlet
+junctions not containing the $F^\prime$ and $F^{\prime \prime}$ layers. The
+slower decay is the prime signature that the supercurrent in the central part
+of these junctions is carried by spin-triplet pairs. The junctions containing
+$F^{\prime}=$ Permalloy are suitable for future experiments where either the
+amplitude of the critical current or the ground-state phase difference across
+the junction is controlled by changing the relative orientations of the
+magnetizations of the $F^{\prime}$ and $F^{\prime \prime}$ layers.",1710.07247v1
+2020-12-16,A tool to predict coercivity in magnetic materials,"Magnetic coercivity is often viewed to be lower in alloys with negligible (or
+zero) values of the anisotropy constant. However, this explains little about
+the dramatic drop in coercivity in FeNi alloys at a non-zero anisotropy value.
+Here, we develop a theoretical and computational tool to investigate the
+fundamental interplay between material constants that govern coercivity in bulk
+magnetic alloys. The two distinguishing features of our coercivity tool are
+that: (a) we introduce a large localized disturbance, such as a spike-like
+magnetic domain, that provides a nucleation barrier for magnetization reversal;
+and (b) we account for magneto-elastic energy -- however small -- in addition
+to the anisotropy and magnetostatic energy terms. We apply this coercivity tool
+to show that the interactions between local instabilities and material
+constants, such as anisotropy and magnetostriction constants, are key factors
+that govern magnetic coercivity in bulk alloys. Using our model, we show that
+coercivity is minimum at the permalloy composition (Fe-21.5Ni-78.5) at which
+the alloy's anisotropy constant is not zero. We systematically vary the values
+of the anisotropy and magnetostriction constants, around the permalloy
+composition, and identify new combinations of material constants at which
+coercivity is small. More broadly, our coercivity tool provides a theoretical
+framework to potentially discover novel magnetic materials with low coercivity.",2012.09320v1
+2021-04-16,Target domains in nanometric Permalloy disks with columnar structure,"We conducted a thorough experimental and numerical study of the micromagnetic
+properties of Permalloy (Ni$_{80}$Fe$_{20}$) microdisks exhibiting target
+domain structures at remanence. Vortex configurations are quite common in such
+microdisks and correspond to an in-plane flux closure configuration of
+cylindrical symmetry with an out-of-plane magnetized core. In contrast, target
+domain configuration are observed in thicker microdisks and are characterized
+by a vortex configuration of the in-plane component of the magnetization
+superposed to an out-of-plane component of magnetization which oscillates as a
+function of the distance to the microdisk center resulting in the formation of
+concentric domains. The ratio of the out-of-plane oscillatory component of the
+magnetization to the in-plane vortex one increases with the thickness of the
+microdisk. Hysteresis loops were measured under in-plane and out-of-plane
+field. The results at remanence and under magnetic field could be interpreted
+by micromagnetic simulations in which the microdisks were described as an
+assembly of partially coupled columns representing the granular nanostructure
+of the films from which the microdisks were patterned. Quite original
+magnetization processes take place in these microdisks exhibiting target domain
+remanent configuration. These include in particular entire flipping of the
+domain configuration and annihilation/creation of ring domains.",2104.07946v1
+2022-05-02,High-Sensitivity Characterization of Ultra-Thin Atomic Layers using Spin-Hall Effect of Light,"Magnetic/non-magnetic/heterostructured ultra-thin films' characterisation is
+highly demanding due to the emerging diverse applications of such films.
+Diverse measurements are usually performed on such systems to infer their
+electrical, optical and magnetic properties. We demonstrate that MOKE-based
+spin-Hall effect of light (SHEL) is a versatile surface characterization tool
+for studying materials' magnetic and dielectric ordering. Using this technique,
+we measure magnetic field dependent complex Kerr angle and the coercivity in
+ultra-thin films of permalloy (Py) and at molybdenum disulphide (MoS$_2$) -
+permalloy (MSPy) hetero-structure interfaces. The measurements are compared
+with standard magneto-optic Kerr effect (MOKE) studies to demonstrate that
+SHEL-MOKE is a practical alternative to the conventional MOKE method, with
+competitive sensitivity. A comprehensive theoretical model and simulation data
+are provided to further strengthen the potential of this simple non-invasive
+optical method. The theoretical model is applied to extract the optical
+conductivity and susceptibility of non-magnetic ultra-thin layers such as
+MoS$_2$ .",2205.00660v2
+2022-06-06,Topological magnetic dipoles and emergent field bundles in a ferromagnetic microstructure by X-ray magnetic vector tomography,"Advanced vector imaging techniques provide us with 3D maps of magnetization
+fields in which topological concepts can be directly applied to describe
+real-space experimental textures in non-ideal geometries. Here, the 3D
+magnetization of a low symmetry permalloy microstructure is obtained by X-ray
+vector magnetic tomography and analysed in detail in terms of topological
+charges and emergent fields. A central asymmetric domain wall with a complex 3D
+structure is observed in which magnetization chirality transitions are mediated
+by Bloch points arranged in several dipoles and a triplet. The ideal spherical
+symmetry of the emergent field of an isolated monopole is severely modified due
+to shape effects of the permalloy microstructure. Emergent field lines
+aggregate into bundles that either connect adjacent Bloch points within a
+topological dipole or tend towards the surface. These bundles may present
+different textures such as helical vortices or half merons, depending on
+asymmetries and confinement, but are constrained by topological charge
+conservation in a given sample volume. This precise description of the
+singularities in realistic systems, enabled by the quantitative experimental
+information on magnetization vector fields, can significantly improve our
+understanding of topological constraints in 3D magnetic systems and provide
+advancements in the design of magnetic devices.",2206.02499v1
+2022-12-24,Spin-to-charge conversion by spin pumping in sputtered polycrystalline Bi$_x$Se$_{1-x}$,"Topological materials are of high interest due to the promise to obtain low
+power and fast memory devices based on efficient spin-orbit torque switching or
+spin-orbit magnetic state read-out. In particular, sputtered polycrystalline
+Bi$_x$Se$_{1-x}$ is one of the materials with more potential for this purpose
+since it is relatively easy to fabricate and has been reported to have a very
+high spin Hall angle. We study the spin-to-charge conversion in
+Bi$_x$Se$_{1-x}$ using the spin pumping technique coming from the ferromagnetic
+resonance in a contiguous permalloy thin film. We put a special emphasis on the
+interfacial properties of the system. Our results show that the spin Hall angle
+of Bi$_x$Se$_{1-x}$ has an opposite sign to the one of Pt. The charge current
+arising from the spin-to-charge conversion is, in contrast, lower than Pt by
+more than one order of magnitude. We ascribe this to the interdiffusion of
+Bi$_x$Se$_{1-x}$ and permalloy and the changes in chemical composition produced
+by this effect, which is an intrinsic characteristic of the system and is not
+considered in many other studies.",2212.12697v2
+2023-02-01,A Brillouin light scattering study of the spin-wave magnetic field dependence in a magnetic hybrid system made of an artificial spin-ice structure and a film underlayer,"We present a combined Brillouin light scattering and micromagnetic simulation
+investigation of the magnetic-field dependent spin-wave spectra in a hybrid
+structure made of permalloy (NiFe) artificial spin-ice (ASI) systems, composed
+of stadium-shaped nanoislands, deposited on the top of an unpatterned permalloy
+film with a nonmagnetic spacer layer. The thermal spin-wave spectra were
+recorded by Brillouin light scattering (BLS) as a function of the magnetic
+field applied along the symmetry direction of the ASI sample. Magneto-optic
+Kerr effect magnetometry was used to measure the hysteresis loops in the same
+orientation as the BLS measurements. The frequency and intensity of several
+spin-wave modes detected by BLS were measured as a function of the applied
+magnetic field. Micromagnetic simulations enabled us to identify the modes in
+terms of their frequency and spatial symmetry and to extract information about
+the existence and strength of the dynamic coupling, relevant only to a few
+modes of a given hybrid system. Using this approach, we suggest a way to
+understand if dynamic coupling between ASI and film modes is present or not,
+with interesting implications for the development of future three-dimensional
+magnonic applications and devices.",2302.00483v1
+2024-02-07,Anatomy of localized edge modes in laterally coupled waveguides,"We present a systematic micromagnetic study of standing spin-wave modes in
+infinitely long Permalloy strips with rectangular cross-section. Using a
+finite-element dynamic-matrix method, we first calculate the eigenfrequencies
+and the corresponding eigenvectors (mode profiles), as a function of the
+in-plane magnetic field applied across the strip. The ferromagnetic resonance
+spectra is computed from the mode profiles, assuming a homogeneous
+radio-frequency excitation, equivalently to an experimental ferromagnetic
+resonance measurement. The investigation of the field-dependent mode profiles
+enables for the classification of the observed resonances, here focusing mostly
+on the true edge mode localized at the vicinity of strip edges. Furthermore, we
+study the mode localization in pairs of 50-nm-thick Permalloy strips as a
+function of the strip width and their lateral separation. For closely spaced
+strips, the spatial profile of the quasi-uniform mode is substantially modified
+due to a significant hybridization with the edge-localized standing spin-wave
+modes of the neighbouring strip. We show that a wide-range-tunability of the
+localized edge-mode resonances can be achieved with a precise control of the
+magnetostatic coupling between the strips. Extreme sensitivity of the edge mode
+frequency on the bias field demonstrates a potential of the edge resonances for
+field sensing. Furthermore, for narrow strips (~100 nm in width), due to the
+reduced number of the allowed confined modes, a field-controllable switching
+between the resonances localized either in the strip center or at the edges of
+the strips can be achieved.",2402.04715v1
+2024-02-15,Standing spin waves in Permalloy-NiO bilayers as a probe of the interfacial exchange coupling,"Ferromagnetic/Antiferromagnetic (FM/AFM) bilayers dynamics have been a recent
+topic of interest due to the interaction occurring at the interface, where the
+magnetic moments of the AFM can be imprinted into the FM, and the exchange bias
+field can affect these dynamics. Here, we investigate Permalloy (Py) and NiO
+(Py/NiO) hybrids and for comparison single Py films in the broad Py thickness
+range varied from few nm to 200 nm by using static (Kerr effect) and dynamic
+(spin waves) measurements along with micromagnetic simulations. We observe
+hybrid modes between uniform (ferromagnetic resonance FMR, n=0) and
+perpendicular standing spin waves (PSSWs, n=1, 2) and a clear enhancement of
+the PSSWs modes frequencies upon interfacing Py with NiO both from experiments
+and simulations. This enhancement becomes less pronounced as the thickness of
+the film increases, demonstrating its interfacial origin rooted in the exchange
+coupling between the FM and AFM layers. Besides, through micromagnetic
+simulations, we investigate and correlate changes in spatial profiles of the
+PSSWs with the interfacial exchange coupling. As the thickness is increased, we
+see that the n=1 and n=2 modes begin to couple with the fundamental FMR mode,
+resulting in asymmetric (with respect the Py layer center) modes. Our results
+suggest that PSSWs detection in a ferromagnet offers a means of probing the
+interfacial exchange coupling with the adjacent AFM layer. Furthermore, the
+controlled spatial symmetry breaking by the AFM layer enables engineering of
+PSSWs with different spatial profiles in the FM.",2402.10292v1
+2011-11-16,Review and Analysis of Measurements of the Spin Hall Effect in Platinum,"Several different experimental techniques have been used in efforts to
+measure the spin Hall conductivity and the spin Hall angle in Pt samples at
+room temperature, with results that disagree by more than a factor of 20, with
+spin Hall conductivities from 2.4 x 10^4 to 5.1 x 10^5 [hbar/(2e)] (Ohm-m)^-1
+and spin Hall angles from 0.0037 to 0.08. We review this work, and analyze
+possible reasons for the discrepancies. We explain that the smallest values for
+the spin Hall angle that have been reported, based on measurements of lateral
+permalloy/copper/platinum devices, are incorrect because the original analyses
+did not properly take into account that copper layers in these devices will
+shunt charge current flowing through adjacent platinum wires, thereby greatly
+reducing the size of the spin-Hall-related signals. We suggest that differences
+between the results for the spin Hall angle found by other experimental
+techniques are primarily a consequence of different assumptions about the value
+of the spin diffusion length in Pt. We present a new measurement of the spin
+diffusion length in Pt within sputtered Pt/permalloy bilayer thin films at room
+temperature, finding 1.4 \pm 0.3 nm, a much smaller value than has generally
+been assumed previously. With this value for the spin diffusion length, the
+previously-discordant results can be brought into much better agreement, with
+the result that the spin Hall conductivities are (1.4 - 3.4) x 10^5 [hbar/(2e)]
+(Ohm-m)^-1 and the spin Hall angles are greater than 0.05. These values are
+sufficiently large that the spin Hall effect in Pt can be used to generate spin
+currents and spin transfer torques strong enough for efficient manipulation of
+magnetic moments in adjacent ferromagnetic layers.",1111.3702v3
+2015-03-13,Paper-based spintronics: magneto-resistivity of permalloy deposited onto paper substrates,"Driven by low-cost, resource abundance and distinct material properties, the
+use of paper in electronics, optics and fluidics is under investigation.
+Considering sensor systems based on magneto-resistance principles (anisotropic,
+giant, tunnel) that are conventionally manufactured onto inorganic
+semiconductor materials, we propose the use of paper substrates for cost
+reduction purposes primarily. In particular, we studied the magneto-resistance
+sensitivity of permalloy (Py:Ni81Fe19) onto paper substrates. In this work, we
+report on our findings with clean room paper (80 g/m2, Rrms = 2.877 {\mu}m, 23%
+surface porosity, latex impregnation, no embossed macro-structure). Here, the
+Py:Ni81Fe19 coating was manufactured by means of a dry process, sputter
+deposition, and spans an area of 10x10 mm2 and a thickness of 70 nm. Employing
+a four-point-probe DC resistivity measurement setup, we investigated the change
+of electrical resistance of Py:Ni81Fe19 under the presence of an oriented
+external magnetic field. In particular, we investigate the magneto-resistive
+change at two configurations: (1) the direction of the magnetic field is
+parallel to the nominal induced electric current and (2) the direction of the
+magnetic field is perpendicular to the electric current. Due to the stochastic
+orientation of the fibers interplaying with the Py:Ni81Fe19 coating, the change
+in magneto-resistance of the overall system at both measurement configurations
+closely corresponds to the classical response of Py:Ni81Fe19 at a +/-45{\deg}
+angle between the direction of electrical current and magnetic field. Using the
+magneto-optic kerr effect, we observed the formation of domain walls at the
+fiber bending locations. Future work will focus on the impact of layer
+thickness, fiber dimensions and structure of magnetic coating on the
+performance of the paper-based Py:Ni81Fe19 magneto-resistors.",1503.04853v2
+2015-08-08,Direct comparison of domain wall behavior in Permalloy nanowires patterned by electron beam lithography and focused ion beam milling,"Nominally identical permalloy nanowires, with widths down to 150 nm, were
+fabricated onto a single electron transparent Si$_{3}$N$_{4}$ membrane using
+electron beam lithography (EBL) and focused ion beam (FIB) milling.
+Transmission electron microscopy (TEM) experiments were performed to compare
+the nanostructures produced by these two techniques in what we believe is the
+first direct comparison of fabrication techniques for nominally identical
+nanowires. Both EBL and FIB methods produced high quality structures with edge
+roughness being of the order of the mean grain size 5 -10 nm observed in the
+continuous films. However, significant grain growth was observed along the
+edges of the FIB patterned nanowires. Lorentz TEM \emph{in situ} imaging was
+carried out to compare the magnetic behavior of the domain walls in the
+patterned nanowires with anti-notches present to pin domain walls. The overall
+process of domain wall pinning and depinning at the anti-notches showed
+consistent behaviour between nanowires fabricated by the two methods with the
+FIB structures having slightly lower characteristic fields compared to the EBL
+wires. However, a significant difference was observed in the formation of a
+vortex structure inside the anti-notches of the EBL nanowires after depinning
+of the domain walls. No vortex structure was seen inside the anti-notches of
+the FIB patterned nanowires. Results from micromagnetic simulations suggest
+that the vortex structure inside the anti-notch can be suppressed if the
+saturation magnetization (M$_{s}$) is reduced along the nanowires edges. Whilst
+the two fabrication methods show that well defined structures can be produced
+for the dimensions considered here, the differences in the magnetic behavior
+for nominally identical structures may be an issue if such structures are to be
+used as conduits for domain walls in potential memory and logic applications.",1508.01910v1
+2016-04-27,Collective spin excitations in bi-component magnonic crystals consisting of bi-layer Permalloy/Fe nanowires,"In the developing field of magnonics,it is very important to achieve
+tailoring of spin wave propagation by both a proper combination of materials
+with different magnetic properties and their nanostructuring on the
+submicrometric scale. We have exploited deep ultra-violet lithography, in
+combination with tilted shadow deposition technique, to fabricate arrays of
+closely spaced bi-layer nanowires (NWs), with separation d=100 nm and
+periodicity a=440 nm, having bottom and top layers made of Permalloy and Iron,
+respectively. The NWs have either rectangular cross section (bottom and upper
+layers of equal width) or L-shaped cross section (upper layer of half width).
+The frequency dispersion of collective spin wave excitations in the above
+bi-layered NWs arrays has been measured by the Brillouin light scattering
+technique while sweeping the wave vector perpendicularly to the wire length
+over three Brillouin zones of the reciprocal space. For the rectangular NWs,
+the lowest frequency fundamental mode, characterized by a quasi- uniform
+profile of the amplitude of the dynamic magnetization across the NW width,
+exhibits a sizeable and periodic frequency dispersion. A similar dispersive
+mode is also present in L-shaped NWs, but the mode amplitude is concentrated in
+the thin side of the NWs. The width and the center frequency of the magnonic
+band associated with the above fundamental modes has been analyzed, showing
+that both can be tuned by varying the external applied field. Moreover, for the
+L-shaped NWs it is shown that there is also a second dispersive mode,at higher
+frequency,characterized by an amplitude concentrated in the thick side of the
+NW. These experimental results have been quantitatively reproduced by an
+original numerical model that includes two-dimensional Green's function of the
+dipole field of the dynamic magnetization and interlayer exchange coupling
+between the layers.",1604.07950v1
+2020-10-13,Tailoring interface mixing and magnetic properties in (111) Permalloy/Pt multilayers,"We present deposition and characterization of multilayers consisting of 20
+repetitions of 15 $\r{A}$ thick permalloy Ni$_{80}$Fe$_{20}$ at. \% (Py) and 5
+$\r{A}$ Pt. The samples were prepared by two different sputter deposition
+methods, namely dc magnetron sputtering (dcMS) and high power impulse magnetron
+sputtering (HiPIMS), that represent low and moderate ionized flux fraction of
+the film forming material, respectively, for deposition of the Py layers. The
+effect of substrate roughness, working gas pressure and sputter power on the
+in-plane uniaxial magnetic anisotropy of the films are studied. The multilayers
+were characterized by X-ray reflectivity and diffraction, and by
+magneto-optical Kerr effect (MOKE). It is shown that HiPIMS deposition produces
+multilayers with unique surface roughness regardless of the substrate surface
+roughness. Multilayers prepared by both dcMS and HiPIMS deposition present a
+strong (111) texture normal to the film plane. The results show that utilizing
+HiPIMS for deposition of the Py layer leads to a minimum interface mixing
+between individual layers compared to dcMS deposition performed at sputter
+power. This is associated with the smooth surface of Py deposited by HiPIMS.
+However, this sharp interface results in higher coercivity and an opening in
+the hard axis hysteresis loops while multilayers with intermixing present well
+defined in-plane uniaxial anisotropy i.e. a linear hard axis. Comparison with
+Py/Cu and Py/CuPt multilayers, prepared under identical conditions using
+HiPIMS, suggests that poor in-plane uniaxial anisotropy is obtained in the
+Py/Pt case, caused by the inverse magnetostriction arising from the large
+lattice mismatch between Py and Pt. The Py/Pt multilayers that exhibit
+interface mixing have a more relaxed interface and thus presents negligible
+inverse magnetostriction and have better defined anisotropy.",2010.06104v3
+1999-02-03,An observation of spin-valve effects in a semiconductor field effect transistor: a novel spintronic device,"We present the first spintronic semiconductor field effect transistor.
+  The injector and collector contacts of this device were made from magnetic
+permalloy thin films with different coercive fields so that they could be
+magnetized either parallel or antiparallel to each other in different applied
+magnetic fields. The conducting medium was a two dimensional electron gas
+(2DEG) formed in an AlSb/InAs quantum well.
+  Data from this device suggest that its resistance is controlled by two
+different types of spin-valve effect: the first occurring at the
+ferromagnet-2DEG interfaces; and the second occuring in direct propagation
+between contacts.",9902057v1
+1999-02-16,Dependence of Magnetic Anisotropy and Magnetoresistance of Ni81Fe19-Films on Annealing,"Permalloy (Py:Ni81Fe19) exhibits an anisotropic magnetoresistance (AMR) which
+is very often used to read magnetic signals from storage devices. Py-films of
+thickness 20nm were prepared by dc-magnetron sputtering in a magnetic field
+onto thermally oxidized Si-wafers and annealed ex situ at temperatures up to
+1000K in order to investigate the dependence of the magnetic anisotropy and the
+AMR on heat treatments. The films exhibit an uniaxial anisotropy after
+preparation which changes during annealing above 520K. The AMR along the former
+magnetically easy axis as well as the corresponding field sensitivity are
+increased by a heat treatment around 700K reaching maxima of about 8% and a
+maximum sensitivity of 1.5%/Oe, respectively. We discuss possible sources for
+the change in anisotropy, i.e. strain effects, inhomogeneities, and changes of
+the local atomic order.",9902222v1
+2000-01-13,Ab-initio Theoretical Description of the Interrelation between Magnetocrystalline Anisotropy and Atomic Short-Range Order,"The cubic lattice symmetry of ferromagnetic homogeneously disordered alloys
+is when a compositional modulation is imposed. This can have a profound
+influence on the magnetocrystalline anisotropy energy (MAE). We describe our
+ab-initio theory of this effect and use the framework of concentration waves
+with the electronic structure described within the spin-polarised relativistic
+Korringa-Kohn-Rostoker coherent-potential approximation. We find that ordering
+produces a 2 order of magnitude increase in the MAE as well as altering the
+equilibrium direction of magnetisation. Using the same theoretical framework we
+also examine directional compositional order produced by magnetic annealing
+with an explicit study of permalloy.",0001181v1
+2000-07-19,Electrical spin injection and detection in a semiconductor. Is it feasible?,"The electrical injection of spin polarized electrons in a semiconductor can
+be achieved in principle by driving a current from a ferromagnetic metal, where
+current is known to be significantly spin polarized, into the semiconductor via
+ohmic conduction. For detection a second ferromagnet can be used as drain. We
+studied submicron lateral spin valve junctions, based on high mobility
+InAs/AlSb two-dimensional electron gas (2DEG), with Ni, Co and Permalloy as
+ferromagnetic electrodes. In the standard geometry it is very difficult to
+separate true spin injection from other effects, including local Hall effect,
+anomalous magnetoresistance (AMR) contribution from the ferromagnetic
+electrodes and weak localization/anti-localization corrections, which can
+closely mimic the signal expected from spin valve effect. The reduction in
+size, and the use of a multiterminal non-local geometry allowed us to reduce
+the unwanted effects to a minimum. Despite all our efforts, we have not been
+able to observe spin injection. However, we find that this 'negative' result in
+these systems is actually consistent with theoretical predictions for spin
+transport in diffusive systems.",0007307v1
+2001-04-23,Interacting circular nanomagnets,"Regular 2D rectangular lattices of permalloy nanoparticles (40 nm in
+diameter) were prepared by the method of the electron lithography. The
+magnetization curves were studied by Hall magnetometry with the compensation
+technique for different external field orientations at 4.2K and 77K. The shape
+of hysteresis curves indicates that there is magnetostatic interaction between
+the particles. The main peculiarity is the existence of remanent magnetization
+perpendicular to easy plain. By numerical simulation it is shown, that the
+character of the magnetization reversal is a result of the interplay of the
+interparticle interaction and the magnetization distribution within the
+particles (vortex or uniform).",0104421v2
+2002-08-12,The role of electron scattering in magnetization relaxation in thin Ni$_{81}$Fe$_{19}$ films,"We observe a strong correlation between magnetization relaxation and
+electrical resistivity in thin Permalloy (Ni$_{81}$Fe$_{19}$, ``Py'') films.
+Electron scattering rates in the films were affected by varying film thickness
+and deposition conditions. This shows that the magnetization relaxation
+mechanism is analogous to ``bulk'' relaxation, where phonon scattering in bulk
+is replaced by surface and defect scattering in thin films. Another interesting
+finding is the increased magnetization damping with Pt layers adjacent to the
+Py films. This is attributed to the strong spin-orbit coupling in Pt, resulting
+in spin-flip scattering of electrons that enter from the Py.",0208207v1
+2002-10-06,Measuring Lateral Magnetic Structure in Thin Films Using Polarized Neutron Reflectometry,"Polarized neutron reflectometry (PNR) has long been applied to measure the
+magnetic depth profile of thin films. In recent years, interest has increased
+in observing lateral magnetic structures in a film. While magnetic arrays
+patterned by lithography and submicron-sized magnetic domains in thin films
+often give rise to off-specular reflections, micron-sized ferromagnetic domains
+on a thin film produce few off-specular reflections and the domain distribution
+information is contained within the specular reflection. In this paper, we will
+first present some preliminary results of off-specular reflectivity from arrays
+of micron-sized permalloy rectangular bars. We will then use specular
+reflections to study the domain dispersion of an exchange-biased Co/CoO bilayer
+at different locations of the hysteresis loop.",0210124v1
+2003-03-08,Current-Driven Magnetic Excitations in Permalloy-Based Multilayer Nanopillars,"We study current-driven magnetization switching in nanofabricated
+Ni84Fe16/Cu/Ni84Fe16 trilayers at 295 K and 4.2 K. The shape of the hysteretic
+switching diagram at low magnetic field changes from 295 K to 4.2 K. The
+reversible behavior at higher field involves two phenomena, a threshold current
+for magnetic excitations closely correlated with the switching current, and a
+peak in differential resistance characterized by telegraph noise, with average
+period that decreases exponentially with current and shifts with temperature.
+We interpret both static and dynamic results at 295 K and 4.2 K in terms of
+thermal activation over a potential barrier, with a current dependent effective
+magnetic temperature.",0303149v2
+2003-09-18,Controllable Josephson current through a pseudo-spin-valve structure,"A thin Co/Cu/Permalloy (Ni$_{80}$Fe$_{20}$) pseudo-spin-valve structure is
+sandwiched between superconducting Nb contacts. When the current is passed
+perpendicular to the plane of the film a Josephson critical current ($I_C$) is
+observed at 4.2 K, in addition to a magnetoresistance (MR) of $\sim$ 0.5 % at
+high bias. The hysteresis loop of the spin-valve structure can be cycled to
+modulate the zero field $I_C$ of the junction in line with the MR measurements.
+These modulations of resistance and $I_C$ occur both smoothly and sharply with
+the applied field. For each type of behaviour there is a strong correlation
+between shape of the MR loops and the $I_C$ modulation.",0309430v1
+2003-09-29,Extraction of domain-specific magnetization reversal for nanofabricated periodic arrays using soft x-ray resonant magnetic scattering,"A simple scheme to extract the magnetization reversals of characteristic
+magnetic domains on nanofabricated periodic arrays from soft x-ray resonant
+magnetic scattering (SXRMS) data is presented. The SXRMS peak intensities from
+a permalloy square ring array were measured with field cycling using circularly
+polarized soft x-rays at the Ni L$_3$ absorption edge. Various SXRMS hysteresis
+loops observed at different diffraction orders enabled the determination of the
+magnetization reversal of each magnetic domain using a simple linear algebra.
+The extracted domain-specific hysteresis loops reveal that the magnetization of
+the domain parallel to the field is strongly pinned, while that of the
+perpendicular domain rotates continuously.",0309672v1
+2003-11-25,Measuring Magnetostriction with an Atomic Force Microscope: Application to Wires in Ballistic Magnetoresistance,"In this study we present a new method of measuring magnetostriction with an
+atomic force microscope adapted for the application magnetic fields. The
+experiment allows us to visualise, in an elegant and educational way how the
+lateral magnetoelastic shape changes take place on the sample surface when a
+magnetic field is applied. We have, furthermore, used this technique to observe
+magnetically induced strains as small as 5*10-8, and have measured Ni,
+permalloy and commercial Cu wires and films, as well as pure Cu and Pt wires,
+where results are in agreement with other methods of measurement. The
+applications are, moreover, relevant to studies of ballistic magnetoresistance,
+where we can draw conclusions involving the effect of the magnetically induced
+strains on magnetoresistance measured at the same time as magnestostriction.",0311567v1
+2004-03-29,Enhancement of the superconducting transition temperature in Nb/Permalloy bilayers by controlling the domain state of the ferromagnet,"In (S/F) hybrids the suppression of superconductivity by the exchange field
+h_ex of the ferromagnet can be partially lifted when different directions of
+h_ex are sampled simultaneously by the Cooper pair. In F/S/F trilayer
+geometries where the magnetization directions of the two F-layers can be
+controlled separately, this leads to the so-called spin switch. Here we show
+that domain walls in a single F-layer yield a similar effect. We study the
+transport properties of Ni_0.8Fe_0.2/Nb bilayers structured in strips of
+different sizes. For large samples a clear enhancement of superconductivity
+takes place in the resistive transition, in the very narrow field range (order
+of 0.5 mT) where the magnetization of the Py layer switches and many domains
+are present. This effect is absent in microstructured samples. Comparison of
+domain wall width \delta_w to the temperature dependent superconductor
+coherence length \xi_S(T) shows that \delta_w ~ \xi_S(T), which means that the
+Cooper pairs sample a large range of different magnetization directions.",0403697v1
+2004-10-09,Current distribution inside Py/Cu lateral spin-valve device,"We have investigated experimentally the non-local voltage signal (NLVS) in
+the lateral permalloy (Py)/Cu/Py spin valve devices with different width of Cu
+stripes. We found that NLVS strongly depends on the distribution of the
+spin-polarized current inside Cu strip in the vicinity of the Py-detector. To
+explain these data we have developed a diffusion model describing spatial (3D)
+distribution of the spin-polarized current in the device. The results of our
+calculations show that NLVS is decreased by factor of 10 due to spin
+flip-scattering occurring at Py/Cu interface. The interface resistivity on
+Py/Cu interface is also present, but its contribution to reduction of NLVS is
+minor. We also found that most of the spin-polarized current is injected within
+the region 30 nm from Py-injector/Cu interface. In the area at Py-detector/Cu
+interface, the spin-polarized current is found to flow mainly close on the
+injector side, with 1/e exponential decay in the magnitude within the distance
+80 nm.",0410228v1
+2005-08-30,Large angle magnetization dynamics measured by time-resolved ferromagnetic resonance,"A time-resolved ferromagnetic resonance technique was used to investigate the
+magnetization dynamics of a 10 nm thin Permalloy film. The experiment consisted
+of a sequence of magnetic field pulses at a repetition rate equal to the
+magnetic systems resonance frequency. We compared data obtained by this
+technique with conventional pulsed inductive microwave magnetometry. The
+results for damping and frequency response obtained by these two different
+methods coincide in the limit of a small angle excitation. However, when
+applying large amplitude field pulses, the magnetization had a non-linear
+response. We speculate that one possible cause of the nonlinearity is related
+to self-amplification of incoherence, known as the Suhl instabilities.",0508708v1
+2005-09-06,Inverse spin switch effects in Ferromagnet / Superconductor hybrids with strong ferromagnets,"In F/S/F trilayers where the magnetization directions of the F layers can be
+controlled separately, it has theoretically been predicted that the
+antiparallel (AP) configuration can have a higher superconducting transition
+temperature T_c than the parallel configuration. This is the so-called spin
+switch, which also experimentally has been found for the case of weak
+ferromagnets. Here we show that strong ferromagnets yield the opposite effect.
+We study the transport properties of F/S/F trilayers with F = Ni_0.80Fe_0.20
+(Permalloy, Py) and S = Nb, structured in strips of different sizes. Using two
+different thicknesses for the Py layers, we can switch in a well-defined way
+between the AP- and P-configurations. In the superconducting transition we find
+a clear increase of the resistance in the AP-state. We ascribe this to enhanced
+reflection of spin-polarized quasiparticles at the S/F interfaces which leads
+to a stronger suppression of superconductivity on the S-side.",0509156v1
+2005-10-31,Time-Resolved Spin Torque Switching and Enhanced Damping in Py/Cu/Py Spin-Valve Nanopillars,"We report time-resolved measurements of current-induced reversal of a free
+magnetic layer in Py/Cu/Py elliptical nanopillars at temperatures T = 4.2 K to
+160 K. Comparison of the data to Landau-Lifshitz-Gilbert macrospin simulations
+of the free layer switching yields numerical values for the spin torque and the
+Gilbert damping parameters as functions of T. The damping is strongly
+T-dependent, which we attribute to the antiferromagnetic pinning behavior of a
+thin permalloy oxide layer around the perimeter of the free layer. This
+adventitious antiferromagnetic pinning layer can have a major impact on spin
+torque phenomena.",0510798v2
+2006-02-09,Anisotropic magnetoresistance and anisotropic tunneling magnetoresistance due to quantum interference in ferromagnetic metal break junctions,"We measure the low-temperature resistance of permalloy break junctions as a
+function of contact size and the magnetic field angle, in applied fields large
+enough to saturate the magnetization. For both nanometer-scale metallic
+contacts and tunneling devices we observe large changes in resistance with
+angle, as large as 25% in the tunneling regime. The pattern of
+magnetoresistance is sensitive to changes in bias on a scale of a few mV. We
+interpret the effect as a consequence of conductance fluctuations due to
+quantum interference.",0602251v2
+2006-02-19,Origin of four-fold anisotropy in square lattices of circular ferromagnetic dots,"We discuss the four-fold anisotropy of in-plane ferromagnetic resonance (FMR)
+field $H_r$, found in a square lattice of circular Permalloy dots when the
+interdot distance $a$ gets comparable to the dot diameter $d$. The minimum
+$H_r$, along the lattice $<11>$ axes, and the maximum, along the $<10>$ axes,
+differ by $\sim$ 50 Oe at $a/d$ = 1.1. This anisotropy, not expected in
+uniformly magnetized dots, is explained by a non-uniform magnetization
+$\bm(\br)$ in a dot in response to dipolar forces in the patterned magnetic
+structure. It is well described by an iterative solution of a continuous
+variational procedure.",0602447v4
+2006-02-22,Soliton pair dynamics in patterned ferromagnetic ellipses,"Confinement alters the energy landscape of nanoscale magnets, leading to the
+appearance of unusual magnetic states, such as vortices, for example. Many
+basic questions concerning dynamical and interaction effects remain unanswered,
+and nanomagnets are convenient model systems for studying these fundamental
+physical phenomena. A single vortex in restricted geometry, also known as a
+non-localized soliton, possesses a characteristic translational excitation mode
+that corresponds to spiral-like motion of the vortex core around its
+equilibrium position. Here, we investigate, by a microwave reflection
+technique, the dynamics of magnetic soliton pairs confined in lithographically
+defined, ferromagnetic Permalloy ellipses. Through a comparison with
+micromagnetic simulations, the observed strong resonances in the subgigahertz
+frequency range can be assigned to the translational modes of vortex pairs with
+parallel or antiparallel core polarizations. Vortex polarizations play a
+negligible role in the static interaction between two vortices, but their
+effect dominates the dynamics.",0602509v1
+2006-06-09,Magnetic resonance studies of the fundamental spin-wave modes in individual submicron Cu/NiFe/Cu perpendicularly magnetized disks,"Spin wave spectra of perpendicularly magnetized disks with trilayers
+consisting of a 100 nm permalloy (Py) layer sandwiched by two Cu layers of 30
+nm, are measured individually with a Magnetic Resonance Force Microscope
+(MRFM). It is demonstrated by 3D micromagnetic simulations that in disks having
+sub-micron size diameters, the lowest energy spin wave mode of the saturated
+state is not spatially uniform but rather is localized at the center of the
+Py/Cu interface in the region of a minimum demagnetizing field.",0606245v3
+2006-07-14,Exchange biasing and electric polarization with YMnO3,"We report on the growth and functional characterization of epitaxial thin
+films of the multiferroic YMnO3. We show that using Pt as a seed layer on
+SrTiO3(111) substrates, epitaxial YMnO3 films (0001) textured are obtained. An
+atomic force microscope has been used to polarize electric domains revealing
+the ferroelectric nature of the film. When a Permalloy layer is grown on top of
+the YMnO3(0001) film, clear indications of exchange bias and enhanced
+coercivity are observed at low temperature. The observation of coexisting
+antiferromagnetism and electrical polarization suggests that the biferroic
+character of YMnO3 can be exploited in novel devices.",0607378v1
+2006-07-24,Magnetoresistance in Thin Permalloy Film (10nm-thick and 30-200nm-wide) Nanocontacts Fabricated by e-Beam Lithography,"In this paper we show spin dependent transport experiments in
+nanoconstrictions ranging from 30 to 200nm. These nanoconstrictions were
+fabricated combining electron beam lithography and thin film deposition
+techniques. Two types of geometries have been fabricated and investigated. We
+compare the experimental results with the theoretical estimation of the
+electrical resistance. Finally we show that the magnetoresistance for the
+different geometries does not scale with the resistance of the structure and
+obtain drops in voltage of 20mV at 20Oe.",0607608v1
+2006-08-24,Observation of standard spin-switch effects in F/S/F trilayers with a strong ferromagnet,"We have measured the superconducting transition temperature T_c of F/S/F
+trilayers using Permalloy (Py=Ni_84 Fe_16) as a strongly polarized
+ferromagnetic material. For a parallel (P) or anti-parallel (AP) alignment of
+the magnetization directions of the outer ferromagnets, we observe a T_c
+difference as large as 20 mK, with a stronger suppression of superconductivity
+in the P state than in the AP state. This behavior is opposite to the recent
+observations of Rusanov et al., Phys. Rev. B 73, 060505 (2006) in Py/Nb/Py
+trilayers, but is consistent with earlier results on trilayers with Ni or CuNi
+alloy as the ferromagnetic material.",0608545v1
+2006-11-27,Nanomagnetic toggle switching of vortex cores on the picosecond time scale,"We present an ultrafast route for a controlled, toggle switching of magnetic
+vortex cores with ultrashort unipolar magnetic field pulses. The switching
+process is found to be largely insensitive to extrinsic parameters, like sample
+size and shape, and it is faster than any field-driven magnetization reversal
+process previously known from micromagnetic theory. Micromagnetic simulations
+demonstrate that the vortex core reversal is mediated by a rapid sequence of
+vortex-antivortex pair-creation and annihilation sub-processes. Specific
+combinations of field pulse strength and duration are required to obtain a
+controlled vortex cores reversal. The operational range of this reversal
+mechanism is summarized in a switching diagram for a 200 nm Permalloy disk.",0611668v2
+2006-12-15,Domain Nucleation and Annihilation in Uniformly Magnetized State under Current Pulses in Narrow Ferromagnetic Wires,"We investigate the current-driven magnetization dynamics in narrow Permalloy
+wires by means of Lorentz microscopy and electron holography. Current pulses
+are found to transform the magnetic structure in the uniformly magnetized state
+below the Curie temperature. A variety of magnetic states including reversed
+magnetic domains are randomly obtained in low probability. The dynamics of
+vortices found in most of observed magnetic states seems to play a key role in
+triggering the magnetization reversal.",0612383v2
+2007-02-05,Demagnetization Protocols for Frustrated Interacting Nanomagnet Arrays,"We report a study of demagnetization protocols for frustrated arrays of
+interacting single domain permalloy nanomagnets by rotating the arrays in a
+changing magnetic field. The most effective demagnetization is achieved by not
+only stepping the field strength down while the sample is rotating, but by
+combining each field step with an alternation in the field direction. By
+contrast, linearly decreasing the field strength or stepping the field down
+without alternating the field direction leaves the arrays with a larger
+remanent magnetic moment. These results suggest that non-monotonic variations
+in field magnitude around and below the coercive field are important for the
+demagnetization process.",0702084v1
+2007-03-21,Ultrafast Vortex-Core Reversal Dynamics in Ferromagnetic Nanodots,"To verify the exact underlying mechanism of ultrafast vortex-core reversal as
+well as the vortex state stability we conducted numerical calculations of the
+dynamic evolution of magnetic vortices in Permalloy cylindrical nanodots under
+an oscillating in-plane magnetic field over a wide range of the frequency and
+amplitude. The calculated results reveal different kinds of the non-trivial
+dynamic responses of vortices to the driving external field. In particular, the
+results offer insight into the 10 ps scale underlying physics of the ulrafast
+vortex-core reversals driven by small amplitude (~10 Oe) in-plane fields. This
+work also provides fundamentals of how to manipulate effectively the dynamical
+switching of the vortex-core orientation.",0703538v1
+2007-03-22,Spin-Torque Ferromagnetic Resonance Measurements of Damping in Nanomagnets,"We measure the magnetic damping parameter a in thin film CoFeB and permalloy
+(Py) nanomagnets at room temperature using ferromagnetic resonance driven by
+microwave frequency spin-transfer torque. We obtain $\alpha_{CoFeB} = 0.014 \pm
+0.003$ and $\alpha_{Py}=0.010 \pm 0.002$, values comparable to measurements for
+extended thin films, but significantly less than the effective damping
+determined previously for similar nanomagnets by fits to time-domain studies of
+large-angle magnetic excitations and magnetic reversal. The greater damping
+found for the large amplitude nanomagnet dynamics is attributed to the
+nonlinear excitation of non-uniform magnetic modes.",0703577v1
+2007-06-12,Graphene Spin Transistor,"Graphitic nanostructures, e.g. carbon nanotubes (CNT) and graphene, have been
+proposed as ideal materials for spin conduction[1-7]; they have long electronic
+mean free paths[8] and small spin-orbit coupling[9], hence are expected to have
+very long spin-scattering times. In addition, spin injection and detection in
+graphene opens new opportunities to study exotic electronic states such as the
+quantum Hall[10,11] and quantum spin Hall[9] states, and spin-polarized edge
+states[12] in graphene ribbons. Here we perform the first non-local four-probe
+experiments[13] on graphene contacted by ferromagnetic Permalloy electrodes. We
+observe sharp switching and often sign-reversal of the non-local resistance at
+the coercive field of the electrodes, indicating definitively the presence of a
+spin current between injector and detector. The non-local resistance changes
+magnitude and sign quasi-periodically with back-gate voltage, and
+Fabry-Perot-like oscillations[6,14,15] are observed, consistent with
+quantum-coherent transport. The non-local resistance signal can be observed up
+to at least T = 300 K.",0706.1597v1
+2007-10-10,Microwave photovoltage and photoresistance effects in ferromagnetic microstrips,"We investigate the dc electric response induced by ferromagnetic resonance in
+ferromagnetic Permalloy (Ni80Fe20) microstrips. The resulting magnetization
+precession alters the angle of the magnetization with respect to both dc and rf
+current. Consequently the time averaged anisotropic magnetoresistance (AMR)
+changes (photoresistance). At the same time the time-dependent AMR oscillation
+rectifies a part of the rf current and induces a dc voltage (photovoltage). A
+phenomenological approach to magnetoresistance is used to describe the distinct
+characteristics of the photoresistance and photovoltage with a consistent
+formalism, which is found in excellent agreement with experiments performed on
+in-plane magnetized ferromagnetic microstrips. Application of the microwave
+photovoltage effect for rf magnetic field sensing is discussed.",0710.1974v3
+2007-11-30,Domain wall pinning and potential landscapes created by constrictions and protrusions in ferromagnetic nanowires,"The potential experienced by transverse domain walls (TDWs) in the vicinity
+of asymmetric constrictions or protrusions in thin Permalloy nanowires is
+probed using spatially resolved magneto-optical Kerr effect measurements. Both
+types of traps are found to act as pinning centers for DWs. The strength of
+pinning is found to depend on the trap type as well as on the chirality of the
+incoming DW; both types of traps are seen to act either as potential wells or
+potential barriers, also depending on the chirality of the DW. Micromagnetic
+simulations have been performed that are in good qualitative agreement with the
+experimental results.",0711.5026v3
+2008-01-30,Time-Resolved X-ray Microscopy of Spin-Torque-Induced Magnetic Vortex Gyration,"Time-resolved X-ray microscopy is used to image the influence of alternating
+high-density currents on the magnetization dynamics of ferromagnetic vortices.
+Spin-torque induced vortex gyration is observed in micrometer-sized permalloy
+squares. The phases of the gyration in structures with different chirality are
+compared to an analytical model and micromagnetic simulations, considering both
+alternating spinpolarized currents and the current's Oersted field. In our case
+the driving force due to spin-transfer torque is about 70% of the total
+excitation while the remainder originates from the current's Oersted field.
+This finding has implications to magnetic storage devices using spin-torque
+driven magnetization switching and domain-wall motion.",0801.4719v1
+2008-02-01,Ultrafast dynamics of a magnetic antivortex - Micromagnetic simulations,"The antivortex is a fundamental magnetization structure which is the
+topological counterpart of the well-known magnetic vortex. We study here the
+ultrafast dynamic behavior of an isolated antivortex in a patterned Permalloy
+thin-film element. Using micromagnetic simulations we predict that the
+antivortex response to an ultrashort external field pulse is characterized by
+the production of a new antivortex as well as of a temporary vortex, followed
+by an annihilation process. These processes are complementary to the recently
+reported response of a vortex and, like for the vortex, lead to the reversal of
+the orientation of the antivortex core region. In addition to its fundamental
+interest, this dynamic magnetization process could be used for the generation
+and propagation of spin waves for novel logical circuits.",0802.0093v1
+2008-04-07,"Energy equilibriation processes of electrons, magnons and phonons on the femtosecond timescale","By means of time-resolved Kerr spectroscopy experiments we relate the energy
+dissipation processes on the femtosecond (electron-spin relaxation time
+$\tau_{el-sp}$) and nanosecond timescale (Gilbert relaxation $\tau_{\alpha}$)
+and compare the results to the first microscopic model, which was proposed by
+Koopmans. For both energy dissipation processes, Elliot-Yafet scattering is
+proposed as the dominant contributor. We controllably manipulate the energy
+dissipation processes by transition metal doping (Pd) and rare earth doping
+(Dy) of a Permalloy film and find that while a change of $\tau_{\alpha}$ of
+more than a factor two is observed, \tau_{el-sp}$ remains constant, contrary to
+the predictions of the model. We explain the discrepancies by relaxation
+channels not considered in the original microscopic model and identify thereby
+the applicability of the model and possible necessary extensions to the model.",0804.0985v1
+2008-05-19,Magnetic dipole induced guided vortex motion,"We present evidence of magnetically controlled guided vortex motion in a
+hybrid superconductor/ferromagnet nanosystem consisting of an Al film on top of
+a square array of permalloy square rings. When the rings are magnetized with an
+in-plane external field H, an array of point-like dipoles with moments
+antiparallel to H, is formed. The resulting magnetic template generates a
+strongly anisotropic pinning potential landscape for vortices in the
+superconducting layer. Transport measurements show that this anisotropy is able
+to confine the flux motion along the high symmetry axes of the square lattice
+of dipoles. This guided vortex motion can be either re-routed by 90 degrees by
+simply changing the dipole orientation or even strongly suppressed by inducing
+a flux-closure magnetic state with very low stray fields in the rings.",0805.2857v1
+2008-07-11,Universal criterion and phase diagram for switching a magnetic vortex core in soft magnetic nanodots,"The universal criterion for ultrafast vortex-core switching between the up-
+and down-core bistates in soft magnetic nanodots was investigated by
+micromagnetic simulations along with analytical calculations. Vortex-core
+switching occurs whenever the velocity of vortex-core motion reaches the
+critical velocity that is expressed as (e.g. m/s for Permalloy), where Aex is
+the exchange stiffness, and is the gyromagnetic ratio. On the basis of the
+above results, phase diagrams for the vortex-core switching event and switching
+times with respect to both the amplitude and frequency of applied circularly
+rotating magnetic field were calculated, which offer practical guidance for
+implementing nanodots in vortex states into future solid-state
+information-storage devices.",0807.1848v5
+2008-10-20,High domain wall velocity at zero magnetic field induced by low current densities in spin-valve nanostripes,"Current-induced magnetic domain wall motion at zero magnetic field is
+observed in the permalloy layer of a spin-valve-based nanostripe using
+photoemission electron microscopy. The domain wall movement is hampered by
+pinning sites, but in between them high domain wall velocities (exceeding 150
+m/s) are obtained for current densities well below $10^{12} \unit{A/m^2}$,
+suggesting that these trilayer systems are promising for applications in domain
+wall devices in case of well controlled pinning positions. Vertical spin
+currents in these structures provide a potential explanation for the increase
+in domain wall velocity at low current densities.",0810.3576v2
+2008-12-29,Vortex dynamics in confined stratified conditions,"We report on linear spin dynamics in the vortex state of the Permalloy dots
+subjected to stratified (magnetic) field. We demonstrate experimentally and by
+simulations the existence of two distinct dynamic regimes corresponding to the
+vortex stable and metastable states. Breaking cylindrical symmetry leads to
+unexpected eigenmodes frequency splitting in the stable state and appearance of
+new eigenmodes in the metastable state above the vortex nucleation field.
+Dynamic response in the metastable state strongly depends on relative
+orientation of the external rf pumping and the bias magnetic fields. These
+findings may be relevant for different vortex states in confined and stratified
+conditions.",0812.4954v1
+2009-03-01,Depinning of domain walls with an internal degree of freedom,"Taking into account the coupling between the position of the wall and an
+internal degree of freedom, namely its phase $\phi$, we examine, in the rigid
+wall approximation, the dynamics of a magnetic domain wall subject to a weak
+pinning potential. We determine the corresponding force-velocity
+characteristics, which display several unusual features when compared to
+standard depinning laws. At zero temperature, there exists a bistable regime
+for low forces, with a logarithmic behavior close to the transition. For weak
+pinning, there occurs a succession of bistable transitions corresponding to
+different topological modes of the phase evolution. At finite temperature, the
+force-velocity characteristics become non-monotonous. We compare our results to
+recent experiments on permalloy nanowires.",0903.0175v1
+2009-03-12,Observation of localized ferromagnetic resonance in a continuous ferromagnetic film via magnetic resonance force microscopy,"We present Magnetic Resonance Force Microscopy (MRFM) measurements of
+Ferromagnetic Resonance (FMR) in a 50 nm thick permalloy film, tilted with
+respect to the direction of the external magnetic field. At small probe-sample
+distances the MRFM spectrum breaks up into multiple modes, which we identify as
+local ferromagnetic resonances confined by the magnetic field of the MRFM tip.
+Micromagnetic simulations support this identification of the modes and show
+they are stabilized in the region where the dipolar tip field has a component
+anti-parallel to the applied field.",0903.2285v1
+2009-05-28,Resonant Nonlinear Damping of Quantized Spin Waves in Ferromagnetic Nanowires,"We use spin torque ferromagnetic resonance to measure the spectral properties
+of dipole-exchange spin waves in permalloy nanowires. Our measurements reveal
+that geometric confinement has a profound effect on the damping of spin waves
+in the nanowire geometry. The damping parameter of the lowest-energy quantized
+spin wave mode depends on applied magnetic field in a resonant way and exhibits
+a maximum at a field that increases with decreasing nanowire width. This
+enhancement of damping originates from a nonlinear resonant three-magnon
+confluence process allowed at a particular bias field value determined by
+quantization of the spin wave spectrum in the nanowire geometry.",0905.4699v2
+2009-05-29,Ferromagnetic resonance linewidth in ultrathin films with perpendicular magnetic anisotropy,"Transition metal ferromagnetic films with perpendicular magnetic anisotropy
+(PMA) have ferromagnetic resonance (FMR) linewidths that are one order of
+magnitude larger than soft magnetic materials, such as pure iron (Fe) and
+permalloy (NiFe) thin films. A broadband FMR setup has been used to investigate
+the origin of the enhanced linewidth in Ni$|$Co multilayer films with PMA. The
+FMR linewidth depends linearly on frequency for perpendicular applied fields
+and increases significantly when the magnetization is rotated into the film
+plane. Irradiation of the film with Helium ions decreases the PMA and the
+distribution of PMA parameters. This leads to a great reduction of the FMR
+linewidth for in-plane magnetization. These results suggest that fluctuations
+in PMA lead to a large two magnon scattering contribution to the linewidth for
+in-plane magnetization and establish that the Gilbert damping is enhanced in
+such materials ($\alpha \approx 0.04$, compared to $\alpha \approx 0.002$ for
+pure Fe).",0905.4779v2
+2009-06-01,Modeling of microwave-assisted switching in micron-sized magnetic ellipsoids,"The microwave assisted magnetisation reversal is modelled in a permalloy
+micron-sized magnetic ellipsoid. Our simulations confirm that this process
+requires less field than magnetisation reversal under a static field. This is
+due to a different reversal mode which in case of the microwave-assisted
+process is always a ripple structure. During the magnetisation reversal two
+stages: nucleation and relaxation are distinguished. The nucleation process is
+governed by spinwave instabilities. The relaxation process is related to the
+domain expansion through domain wall propagation determined by the precessional
+motion of magnetic moments in the center of the domain walls. As a consequence,
+the switching time is a complex oscillating function of the microwave
+frequency.",0906.0263v1
+2009-09-30,Phase diagram of magnetic configurations for soft magnetic nanodots of circular and elliptical shape obtained by micromagnetic simulation,"Magnetic disks or dots of soft magnetic material of sub-micron dimensions may
+have as the lowest energy magnetic configuration a single-domain structure,
+with magnetization either perpendicular of parallel to the plane, or else may
+form magnetic vortices. The properties of these vortices may be used to encode
+data bits, in magnetic memory applications. In the present work the OOMMF code
+was used to compute by micromagnetic simulation the energy and the
+magnetization of circular and elliptical nanodots of permalloy. For the
+elliptical magnetic dots the analysis was made for variable thickness and
+length of major axis, keeping a 2:1 axis ratio. From the simulations, a phase
+diagram was constructed, where the ground state configurations of the nanodots
+are represented in a diagram of nanodot height versus length of the major axis
+$2a$ of the ellipse. The phase diagram obtained includes regions with one and
+two vortices; it is similar, but more complex than that derived using a
+numerical scaling approach, since it includes configurations with lateral
+vortices. These diagrams are useful as guides for the choice of dimensions of
+elliptical nanodots for practical applications.",0909.5686v1
+2009-10-16,Transverse instabilities of multiple vortex chains in superconductor-ferromagnet bilayers,"Using scanning tunneling microscopy and Ginzburg-Landau simulations we
+explore vortex configurations in magnetically coupled NbSe$_2$-Permalloy
+superconductor-ferromagnet bilayer. The Permalloy film with stripe domain
+structure induces periodic local magnetic induction in the superconductor
+creating a series of pinning-antipinning channels for externally added magnetic
+flux quanta. Such laterally confined Abrikosov vortices form quasi-1D arrays
+(chains). The transitions between multichain states occur through propagation
+of kinks at the intermediate fields. At high fields we show that the system
+becomes non-linear due to a change in both the number of vortices and the
+confining potential. The longitudinal instabilities of the resulting vortex
+structures lead to vortices `levitating' in the anti-pinning channels.",0910.3030v1
+2009-11-10,Spin-wave propagation in a microstructured magnonic crystal,"Transmission of microwave spin waves through a microstructured magnonic
+crystal in the form of a permalloy waveguide of a periodically varying width
+was studied experimentally and theoretically. The spin wave characteristics
+were measured by spatially-resolved Brillouin light scattering microscopy. A
+rejection frequency band was clearly observed. The band gap frequency was
+controlled by the applied magnetic field. The measured spin-wave intensity as a
+function of frequency and propagation distance is in good agreement with a
+model calculation.",0911.1920v1
+2009-11-11,Temperature dependent nucleation and annihilation of individual magnetic vortices,"We studied the temperature dependence of the magnetization reversal in
+individual submicron permalloy disks with micro-Hall and bend-resistance
+magnetometry. The nucleation field exhibits a nonmonotonic dependence with
+positive and negative slopes at low and high temperatures, respectively, while
+the annihilation field monotonically decreases with increasing temperature, but
+with distinctly different slopes at low and high temperatures. Our analysis
+suggests that at low temperatures vortex nucleation and annihilation proceeds
+via thermal activation over an energy barrier, while at high temperatures they
+are governed by a temperature dependence of the saturation magnetization.",0911.2267v1
+2010-01-20,Precise probing spin wave mode frequencies in the vortex state of circular magnetic dots,"We report on detailed broadband ferromagnetic resonance measurements of
+azimuthal and radial spin wave excitations in circular Permalloy dots in the
+vortex ground state. Dots with aspect ratio (Beta =height over radius) varied
+from 0.03 to 0.1 were explored. We found that for Beta exceeding approximately
+0.05, variation of the spin wave eigenfrequencies with Beta deviates from the
+predicted dependence. The frequency splitting of two lowest azimuthal modes was
+observed. The experimentally observed dependence of the frequency splitting on
+beta was reasonably well described by dynamic splitting model accounting the
+spin-waves and, vortex gyrotropic mode interaction.",1001.3605v1
+2010-05-07,Non-adiabatic spin torque investigated using thermally activated magnetic domain wall dynamics,"Using transmission electron microscopy, we investigate the thermally
+activated motion of domain walls (DWs) between two positions in permalloy
+(Ni80Fe20) nanowires at room temperature. We show that this purely thermal
+motion is well described by an Arrhenius law, allowing for a description of the
+DW as a quasi-particle in a 1D potential landscape. By injecting small
+currents, the potential is modified, allowing for the determination of the
+non-adiabatic spin torque: the non-adiabatic coefficient is 0.010 +/- 0.004 for
+a transverse DW and 0.073 +/- 0.026 for a vortex DW. The larger value is
+attributed to the higher magnetization gradients present.",1005.1168v1
+2010-06-02,Magnetization pinning in conducting films demonstrated using broadband ferromagnetic resonance,"The broadband microstrip ferromagnetic resonance technique has been applied
+for detection and characterization of a magnetic inhomogeneity in a film
+sample. In the case of a 100nm thick Permalloy film an additional magnetically
+depleted top sub-layer, practically unidentifiable by the conventional
+ferromagnetic resonance setup, has been detected and characterized. These
+results have been confirmed by Brillouin light scattering spectroscopy
+revealing the fact that the optical properties of the additional sub-layer do
+not differ much from those of the bulk of the film. Subsequent characterization
+of a large number of other presumably single-layer films with thicknesses in
+the range 30-100nm using the same ferromagnetic resonance technique also
+revealed the same effect.",1006.0331v1
+2010-10-08,"A unified first-principles study of Gilbert damping, spin-flip diffusion and resistivity in transition metal alloys","Using a formulation of first-principles scattering theory that includes
+disorder and spin-orbit coupling on an equal footing, we calculate the
+resistivity $\rho$, spin flip diffusion length $l_{sf}$ and the Gilbert damping
+parameter $\alpha$ for Ni$_{1-x}$Fe$_x$ substitutional alloys as a function of
+$x$. For the technologically important Ni$_{80}$Fe$_{20}$ alloy, permalloy, we
+calculate values of $\rho = 3.5 \pm 0.15$ $\mu$Ohm-cm, $l_{sf}=5.5 \pm 0.3$ nm,
+and $\alpha= 0.0046 \pm 0.0001$ compared to experimental low-temperature values
+in the range $4.2-4.8$ $\mu$Ohm-cm for $\rho$, $5.0-6.0$ nm for $l_{sf}$, and
+$0.004-0.013$ for $\alpha$ indicating that the theoretical formalism captures
+the most important contributions to these parameters.",1010.1626v3
+2011-02-01,One-dimentional magnonic crystal as a medium with magnetically tunable disorder on a periodical lattice,"We show that periodic magnetic nanostructures (magnonic crystals) represent
+an ideal system for studying excitations on disordered periodical lattices
+because of the possibility of controlled variation of the degree of disorder by
+varying the applied magnetic field. Ferromagnetic resonance (FMR) data
+collected inside minor hysteresis loops for a periodic array of Permalloy
+nanowires of alternating width and magnetic force microscopy images of the
+array taken after running each of these loops were used to establish convincing
+evidence that there is a strong correlation between the type of FMR response
+and the degree of disorder of the magnetic ground state. We found two types of
+dynamic responses: anti-ferromagnetic (AFM) and ferromagnetic (FM), which
+represent collective spin wave modes or collective magnonic states. Depending
+on the history of sample magnetization either AFM or FM state is either the
+fundamental FMR mode or represents a state of a magnetic defect on the
+artificial crystal. A fundamental state can be transformed into a defect one
+and vice versa by controlled magnetization of the sample.",1102.0069v1
+2011-02-09,Enhancement of the response of non-uniform resonance modes of a nanostructure in the Picoprobe microwave-current injection ferromagnetic resonance,"The non-uniform standing spin-wave modes in thin magnetic films and
+nanostructures provide important information about surfaces and buried
+interfaces. Very often they are lacking in the recorded ferromagnetic resonance
+spectra for symmetry reasons. In this work we experimentally demonstrate that
+by direct injection of microwave currents into an array of Permalloy
+nanostripes using a microscopic microwave coaxial to coplanar adaptor one can
+efficiently excite non-uniform standing spin wave modes with odd symmetry. The
+proposed method is quick and allows easy spatial mapping of magnetic properties
+with the resolution down to 100 microns. We have validated this method using an
+example from a periodical array of nanostripes. The results from direct current
+injection are compared to that of microstrip-based FMR measurements.",1102.1805v2
+2011-02-22,Ab-initio calculation of the Gilbert damping parameter via linear response formalism,"A Kubo-Greenwood-like equation for the Gilbert damping parameter $\alpha$ is
+presented that is based on the linear response formalism. Its implementation
+using the fully relativistic Korringa-Kohn-Rostoker (KKR) band structure method
+in combination with Coherent Potential Approximation (CPA) alloy theory allows
+it to be applied to a wide range of situations. This is demonstrated with
+results obtained for the bcc alloy system Fe$_x$Co$_{1-x}$ as well as for a
+series of alloys of permalloy with 5d transition metals.
+  To account for the thermal displacements of atoms as a scattering mechanism,
+an alloy-analogy model is introduced. The corresponding calculations for Ni
+correctly describe the rapid change of $\alpha$ when small amounts of
+substitutional Cu are introduced.",1102.4551v1
+2011-04-19,Spin relaxation mechanism in Silver nanowires covered with MgO protection layer,"Spin-flip mechanism in Ag nanowires with MgO surface protection layers has
+been investigated by means of nonlocal spin valve measurements using
+Permalloy/Ag lateral spin valves. The spin flip events mediated by surface
+scattering are effectively suppressed by the MgO capping layer. The spin
+relaxation process was found to be well described in the framework of
+Elliott-Yafet mechanism and then the probabilities of spin-filp scattering for
+phonon or impurity mediated momentum scattering is precisely determined in the
+nanowires. The temperature dependent spin-lattice relaxation follows the
+Bloch-Gr\""uneisen theory and falls on to a universal curve for the monovalent
+metals as in the Monod and Beuneu scaling determined from the conduction
+electron spin resonance data for bulk.",1104.3718v2
+2011-05-27,Mechanisms of nonlinear spin-wave emission from a microwave driven nanocontact,"We present a micromagnetic study of linear and nonlinear spin-wave modes
+excited in an extended permalloy thin film by a microwave driven nanocontact.
+We show that the linear mode having the frequency equal to the excitation
+frequency (f) is driven by the ac Oersted field component perpendicular to the
+static external field (applied in-plane of the sample). The nonlinear mode with
+the frequency f /2 is excited as an independent eigenmode within a parametric
+longitudinal pumping process (due ac Oersted field component parallel to the
+bias field). Spectral positions of those modes are determined both in the space
+and phase domain. The results are important for the transfer of information
+coded into spin-waves between nanocontacts, and for synchronization of spin
+transfer torque nano-oscillators.",1105.5512v1
+2011-06-21,All-Optical Excitation and Detection of Picosecond Dynamics of Ordered Arrays of Nanomagnets with Varying Areal Density,"We have demonstrated optical excitation and detection of collective
+precessional dynamics in arrays of coupled Ni80Fe20 (permalloy) nanoelements
+with systematically varying areal density by an all-optical time-resolved Kerr
+microscope. We have applied this technique to precisely determine three
+different collective regimes in these arrays. At very high areal density, a
+single uniform collective mode is observed where the edge modes of the
+constituent elements are suppressed. At intermediate areal densities, three
+nonuniform collective modes appear and at very low areal density, we observe
+noncollective dynamics and only the centre and edge modes of the constituent
+elements appear.",1106.4113v2
+2011-10-04,Observation of non-linear magnetic vortex gyration by X-ray microscopy and micromagnetic simulations,"Magnetic vortex gyration in a 500 nm wide, 50 nm thick Permalloy square
+platelet was investigated using time-resolved scanning transmission x-ray
+microscopy and micromagnetic simulations. The response of the vortex core on an
+in-plane oscillating magnetic field was studied as a function of the excitation
+frequency and amplitude. Non-linear behavior was observed in the form of a
+redshift of the gyrotropic resonance. I.e., when the excitation amplitude was
+increased, the resonance frequency was found to decrease. The nonlinearity is
+in agreement with extensive micromagnetic simulations. This work complements
+previous reports on thinner nanostructures where a frequency blueshift was
+observed.",1110.0828v1
+2011-10-12,First-principles study of the spin-mixing conductance in Pt/Ni$_{81}$Fe$_{19}$ junctions,"Based on the spin-pumping theory and first-principles calculations, the
+spin-mixing conductance (SMC) is theoretically studied for Pt/Permalloy
+(Ni$_{81}$Fe$_{19}$, Py) junctions. We evaluate the SMC for ideally clean Pt/Py
+junctions and examine the effects of interface randomness. We find that the SMC
+is generally enhanced in the presence of interface roughness as compared to the
+ideally clean junctions. Our estimated SMC is in good quantitative agreement
+with the recent experiment for Pt/Py junctions. We propose possible routes to
+increase the SMC in Pt/Py junctions by depositing a foreign magnetic metal
+layer in Pt, offering guidelines for designing the future spintronic devices.",1110.2546v1
+2011-11-18,Exchange Bias Induced by the Fe3O4 Verwey transition,"We present a study of the exchange bias in different configurations of V2O3
+thin films with ferromagnetic layers. The exchange bias is accompanied by a
+large vertical shift in the magnetization. These effects are only observed when
+V2O3 is grown on top of Ni80Fe20 permalloy. The magnitude of the vertical shift
+is as large as 60% of the total magnetization which has never been reported in
+any system. X-Ray diffraction studies show that the growth conditions promote
+the formation of a ferrimagnetic Fe3O4 interlayer. The change in the easy
+magnetization axis of Fe3O4 across the Verwey transition at 120 K is correlated
+with the appearance of exchange bias and vertical shift in magnetization. Both
+phenomena disappear above 120 K, indicating for the first time a direct
+relationship between the magnetic signature of the Verwey transition and
+exchange bias.",1111.4255v2
+2011-11-20,Detection of picosecond magnetization dynamics of 50 nm magnetic dots down to the single dot regime,"We report an all-optical time-domain detection of picosecond magnetization
+dynamics of arrays of 50 nm Ni80Fe20 (permalloy) dots down to the single
+nanodot regime. In the single nanodot regime the dynamics reveals one dominant
+resonant mode corresponding to the edge mode of the 50 nm dot with slightly
+higher damping than that of the unpatterned thin film. With the increase in
+areal density of the array both the precession frequency and damping increases
+significantly due to the increase in magnetostatic interactions between the
+nanodots and a mode splitting and sudden jump in apparent damping are observed
+at an edge-to-edge separation of 50 nm.",1111.4625v1
+2012-01-02,Localized domain-wall excitations in patterned magnetic dots probed by broadband ferromagnetic resonance,"We investigate the magnetization dynamics in circular Permalloy dots with
+spatially separated magnetic vortices interconnected by domain walls (double
+vortex state). We identify a novel type of quasi one-dimensional (1D) localised
+spin wave modes confined along domain walls, connecting each of two vortex
+cores with two edge half-antivortices. Variation of the mode eigenfrequencies
+with the dot size is in quantitative agreement with the developed model, which
+considers a dipolar origin of the localized 1D spin waves or so-called
+Winter\'s magnons [J.M. Winter, Phys.Rev. 124, 452 (1961)]. These spin waves
+are analogous to the displacement waves of strings, and could be excited in a
+wide class of patterned magnetic nanostructures possessing domain walls, namely
+in triangular, square, circular or elliptic magnetic dots.",1201.0482v1
+2012-02-03,Domain - wall - induced magnetoresistance in pseudo spin-valve/superconductor hybrid structures,"We have studied the interaction between magnetism and superconductivity in a
+pseudo-spin-valve structure consisting of a Co/Cu/Py/Nb layer sequence. We are
+able to control the magnetization reversal process and monitor it by means of
+the giant magnetoresistance effect during transport measurements. By placing
+the superconducting Nb-film on the top of the permalloy (Py) electrode instead
+of putting it in between the two ferromagnets, we minimize the influence of
+spin scattering or spin accumulation onto the transport properties of Nb.
+Magnetotransport data reveal clear evidence that the stray fields of domain
+walls (DWs) in the pseudo-spin-valve influence the emerging superconductivity
+close to the transition temperature by the occurrence of peak-like features in
+the magneto-resistance characteristic. Direct comparison with magnetometry data
+shows that the resistance peaks occur exactly at the magnetization reversal
+fields of the Co and Py layers, where DWs are generated. For temperatures near
+the superconducting transition the amplitude of the DW-induced
+magnetoresistance increases with decreasing temperature, reaching values far
+beyond the size of the giant magnetoresistive response of our structure in the
+normal state.",1202.0715v1
+2012-02-20,Stability of Spinmotive Force in Perpendicularly Magnetized Nanowires under High Magnetic Fields,"Spinmotive force induced by domain wall motion in perpendicularly magnetized
+nanowires is numerically demonstrated. We show that using nanowires with large
+magnetic anisotropy can lead to a high stability of spinmotive force under
+strong magnetic fields. We observe spinmotive force in the order of tens of
+microvolt in a multilayered Co/Ni nanowire and in the order of several hundred
+microvolt in a FePt nanowire; the latter is two orders of magnitude greater
+than that in permalloy nanowires reported previously. The narrow structure and
+low mobility of a domain wall under magnetic fields in perpendicularly
+magnetized nanowires permits downsizing of spinmotive force devices.",1202.4256v2
+2012-02-25,Magnetization states and switching in narrow-gapped ferromagnetic nanorings,"We study permalloy nanorings that are lithographically fabricated with narrow
+gaps that break the rotational symmetry of the ring while retaining the vortex
+ground state, using both micromagnetic simulations and magnetic force
+microscopy (MFM). The vortex chirality in these structures can be readily set
+with an in-plane magnetic field and easily probed by MFM due to the field
+associated with the gap, suggesting such rings for possible applications in
+storage technologies. We find that the gapped ring edge characteristics (i.e.,
+edge profile and gap shape) are critical in determining the magnetization
+switching field, thus elucidating an essential parameter in the controls of
+devices that might incorporate such structures.",1202.5596v1
+2012-03-01,Phase diagram of magnetic domain walls in spin valve nano-stripes,"We investigate numerically the transverse versus vortex phase diagram of
+head-to-head domain walls in Co/Cu/Py spin valve nano-stripes (Py: Permalloy),
+in which the Co layer is mostly single domain while the Py layer hosts the
+domain wall. The range of stability of the transverse wall is shifted towards
+larger thickness compared to single Py layers, due to a magnetostatic screening
+effect between the two layers. An approached analytical scaling law is derived,
+which reproduces faithfully the phase diagram.",1203.0192v2
+2012-03-22,A Numerical Model of Crossed Andreev Reflection and Charge Imbalance,"We present a numerical model of local and nonlocal transport properties in a
+lateral spin valve structure consisting of two magnetic electrodes in contact
+with a third perpendicular superconducting electrode. By considering the
+transport paths for a single electron incident at the local F/S interface - in
+terms of probabilities of crossed or local Andreev reflection, elastic
+cotunneling or quasiparticle transport - we show that this leads to nonlocal
+charge imbalance. We compare this model with experimental data from an
+aluminum-permalloy (Al/Py) lateral spin valve geometry device and demonstrate
+the effectiveness of this simple approach in replicating experimental behavior.",1203.4949v2
+2012-03-28,Spin Hall Angle Quantification from Spin Pumping and Microwave Photoresistance,"We present a method to quantify the spin Hall angle (SHA) with spin pumping
+and microwave photoresistance measurements. With this method, we separate the
+inverse spin Hall effect (ISHE) from other unwanted effects for permalloy/Pt
+bilayers using out-of-plane microwave excitation. Through microwave
+photoresistance measurements, the in- and out-of-plane precessing angles of the
+magnetization are determined and enabled for the exact determination of the
+injected pure spin current. This method is demonstrated with an almost perfect
+Lorentz line-shape for the obtained ISHE signal and the frequency independent
+SHA value as predicted by theory. By varying the Pt thickness, the SHA and
+spin-diffusion length of Pt is quantified as 0.012 (0.001) and 8.3 (0.9) nm,
+respectively.",1203.6175v1
+2012-07-26,Spin-orbit-coupling induced domain-wall resistance in diffusive ferromagnets,"We investigate diffusive transport through a number of domain wall (DW)
+profiles of the important magnetic alloy Permalloy taking into account
+simultaneously noncollinearity, alloy disorder, and spin-orbit coupling fully
+quantum mechanically, from first principles. In addition to observing the known
+effects of magnetization mistracking and anisotropic magnetoresistance, we
+discover a not-previously identified contribution to the resistance of a DW
+that comes from spin-orbit-coupling-mediated spin-flip scattering in a textured
+diffusive ferromagnet. This adiabatic DW resistance, which should exist in all
+diffusive DWs, can be observed by varying the DW width in a systematic fashion
+in suitably designed nanowires.",1207.6277v2
+2012-08-24,Domain-wall induced large magnetoresistance effects at zero applied field in ballistic nanocontacts,"We determine magnetoresistance effects in stable and clean permalloy
+nanocontacts of variable cross-section, fabricated by UHV deposition and
+in-situ electromigration. To ascertain the magnetoresistance (MR) effects
+originating from a magnetic domain wall, we measure the resistance values with
+and without such a wall at zero applied field. In the ballistic transport
+regime, the MR ratio reaches up to 50% and exhibits a previously unobserved
+sign change. Our results can be reproduced by recent atomistic calculations for
+different atomic configurations of the nanocontact, highlighting the importance
+of the detailed atomic arrangement for the MR effect.",1208.4985v1
+2012-11-02,Dynamic Spin Injection into Chemical Vapor Deposited Graphene,"We demonstrate dynamic spin injection into chemical vapor deposition (CVD)
+grown graphene by spin pumping from permalloy (Py) layers. Ferromagnetic
+resonance measurements at room temperature reveal a strong enhancement of the
+Gilbert damping at the Py/graphene interface, exceeding that observed in even
+Py/platinum interfaces. Similar results are also shown on Co/graphene layers.
+This enhancement in the Gilbert damping is understood as the consequence of
+spin pumping at the interface driven by magnetization dynamics. Our
+observations suggest a strong enhancement of spin-orbit coupling in CVD
+graphene, in agreement with earlier spin valve measurements.",1211.0492v1
+2012-11-07,Dipolar coupling between nanopillar spin valves and magnetic quantum cellular automata arrays,"We experimentally demonstrate magnetostatic coupling between a nanopillar
+pseudo spin valve structure and a linear array of dipole coupled Permalloy
+nanomagnets. Using magnetic force microscopy, we study the interaction between
+the spin valve and the first element of the array, and present evidence that
+the nanomagnet couples with the hard layer of the spin valve for two spin
+valves with distinctly different composition. Our study includes a statistical
+analysis of antiferromagnetic order within the linear array, and provides
+insight into the range of behavior that these arrays can display. These results
+bear directly on the design of magnetic quantum cellular automata (MQCA) logic
+devices, showing that multilayer devices can couple to simple nanomagnets.
+Redesigning the hard layer of the magnetoresistive devices would make them
+operational as an electronic input that will allow integration of MQCA networks
+in complex electronic circuitry.",1211.1536v2
+2012-12-07,Brillouin Light Scattering Spectra as local Temperature Sensors for Thermal Magnons and Acoustic Phonons,"We demonstrate the use of the micro-Brillouin light scattering (micro-BLS)
+technique as a local temperature sensor for magnons in a Permalloy thin film
+and phonons in the glass substrate. A systematic shift in the frequencies of
+two thermally excited perpendicular standing spin wave modes as the film is
+uniformly heated allows us to achieve a temperature resolution better than 2.5
+K. We demonstrate that the micro-BLS spectra can be used to measure the local
+temperatures of phonons and magnons across a thermal gradient. Such local
+temperature sensors are useful for investigating spin caloritronic and thermal
+transport phenomena in general.",1212.1520v2
+2012-12-12,Giant magnetoimpedance of composite wires with an insulation layer,"Composite wires with a three-layered structure exhibit a large giant
+magneto-impedance (GMI) effect, which can be used in sensitive magnetic field
+sensors. To further investigate the origin of the GMI effect, composite wires
+consisting of a highly conductive copper core, a silicon dioxide layer and an
+outer Permalloy shell were prepared by radio frequency (RF) magnetron
+sputtering. The GMI ratio was measured at various driving current frequencies
+and with different insulating layer thicknesses. A theoretical model by
+coupling the Maxwell equations to the Landau-Lifschitz-Gilbert equation was
+developed to investigate the composite wire impedance and its dependence on
+external magnetic field, current frequency and insulating layer thickness.
+Experimental results corroborate the theoretical model.",1212.2745v2
+2013-01-10,"Comment on ""Physical Origin and Generic Control of Magnonic Band Gaps of Dipole-Exchange Spin Waves in Width-Modulated Nanostrip Waveguides"" [K.-S. Lee, D.-S. Han, and S.-K. Kim, PRL 102, 127202 (2009), arXiv:0811.0411]","In Ref. [PRL 102, 127202 (2009)] Lee et al. reported the existence of large
+magnonic bandgaps in one-dimensional width-modulated Permalloy nanostripe
+waveguides based on OOMMF simulations. However, as the symmetry of the magnetic
+field pulse they applied to excite the spin waves (SWs) was not general, the
+entire set of SW branches with A symmetry was omitted from the magnonic band
+structures (see below). This omission has unfortunately led to misleading
+conclusions of, for instance, the number, width and position of the bandgaps.
+We present here the full band structure based on three different theoretical
+approaches that gave consistent predictions, thus corroborating the methods
+employed, namely, a microscopic approach, OOMMF simulations, and a method based
+on the linearized Landau-Lifshitz equation. Further, we provide a physical
+interpretation using group theory.",1301.2036v1
+2013-05-28,Magnonic band gaps in waveguides with a periodic variation of the saturation magnetization,"We present a micromagnetic analysis of spin-wave propagation in a magnonic
+crystal realized as a permalloy spin-wave waveguide with a spatial periodical
+variation of its saturation magnetization. Frequency band gaps were clearly
+observed in the spin-wave transmission spectra and their origin is traced back
+to an overlap of individual band gaps of the fundamental and the higher order
+spin-wave width modes. The control of the depth, width and the position in
+frequency and space of the rejection band gaps by the width areas with a
+reduced magnetization and by the modulation level, are discussed in this study.",1305.6619v1
+2013-09-09,Quantitative stray field imaging of a magnetic vortex core,"Thin-film ferromagnetic disks present a vortex spin structure whose dynamics,
+added to the small size (~10 nm) of their core, earned them intensive study.
+Here we use a scanning nitrogen-vacancy (NV) center microscope to
+quantitatively map the stray magnetic field above a 1 micron-diameter disk of
+permalloy, unambiguously revealing the vortex core. Analysis of both
+probe-to-sample distance and tip motion effects through stroboscopic
+measurements, allows us to compare directly our quantitative images to
+micromagnetic simulations of an ideal structure. Slight perturbations with
+respect to the perfect vortex structure are clearly detected either due to an
+applied in-plane magnetic field or imperfections of the magnetic structures.
+This work demonstrates the potential of scanning NV microscopy to map tiny
+stray field variations from nanostructures, providing a nanoscale,
+non-perturbative detection of their magnetic texture.",1309.2171v2
+2013-09-24,Influence of heat flow directions on Nernst effects in Py/Pt bilayers,"We investigated the voltages obtained in a thin Pt strip on a Permalloy film
+which was subject to in-plane temperature gradients and magnetic fields. The
+voltages detected by thin W-tips or bond wires showed a purely symmetric effect
+with respect to the external magnetic field which can be fully explained by the
+planar Nernst effect (PNE). To verify the influence of the contacts
+measurements in vacuum and atmosphere were compared and gave similar results.
+We explain that a slightly in-plane tilted temperature gradient only shifts the
+field direction dependence but does not cancel out the observed effects.
+Additionally, the anomalous Nernst effect (ANE) could be induced by using thick
+Au-tips which generated a heat current perpendicular to the sample plane. The
+effect can be manipulated by varying the temperature of the Au-tips. These
+measurements are discussed concerning their relevance in transverse spin
+Seebeck effect measurements.",1309.6237v2
+2013-10-17,Electrical Detection of Direct and Alternating Spin Current Injected from a Ferromagnetic Insulator into a Ferromagnetic Metal,"We report room temperature electrical detection of spin injection from a
+ferromagnetic insulator (YIG) into a ferromagnetic metal (Permalloy, Py).
+Non-equilibrium spins with both static and precessional spin polarizations are
+dynamically generated by the ferromagnetic resonance of YIG magnetization, and
+electrically detected by Py as dc and ac spin currents, respectively. The dc
+spin current is electrically detected via the inverse spin Hall effect of Py,
+while the ac spin current is converted to a dc voltage via the spin
+rectification effect of Py which is resonantly enhanced by dynamic exchange
+interaction between the ac spin current and the Py magnetization. Our results
+reveal a new path for developing insulator spintronics, which is distinct from
+the prevalent but controversial approach of using Pt as the spin current
+detector.",1310.4840v1
+2013-10-23,Exchange-dominated Standing Spin Wave Excitations under microwave irradiation in Ni80Fe20 Thin Films,"We investigated the microwave-assisted DC voltages of ferromagnetic
+resonances and exchangedominated standing spin wave excitations in two
+different in-plane magnetized permalloy thin films via homodyne detection. The
+line shapes of ferromagnetic resonance spectra and the dispersion curves of
+ferromagnetic resonance and standing spin wave are in agreement of previous
+studies, while further investigations of DC voltage spectra for these two
+excitations reveal that 1. unlike ferromagnetic resonance signals, the
+anti-symmetrical line shapes of standing spin wave excitations are not depend
+on the electromagnetic relative phase of assisted microwave, and 2. linewidths
+of their DC voltage spectra are distinct. The complicated spin dynamics of
+standing spin wave is consequently discussed by applying
+Landau-Lifshitz-Gilbert equation in term of exchange interaction.",1310.6108v1
+2013-11-04,Non-reciprocal Oersted field contribution to the current-induced frequency shift of magnetostatic surface waves,"The influence of an electrical current on the propagation of magnetostatic
+surface waves is investigated in a relatively thick (40 nm) permalloy film both
+experimentally and theoretically. Contrary to previously studied thinner films
+where the dominating effect is the current-induced spin-wave Doppler shift, the
+magnetic field generated by the current (Oersted field) is found to induce a
+strong non-reciprocal frequency shift which overcompensates the Doppler shift.
+The measured current induced frequency shift is in agreement with the developed
+theory. The theory relates the sign of of the frequency shift to the spin wave
+modal profiles. The good agreement between the experiment and the theory
+confirms a recent prediction of a counter-intuitive mode localization for
+magnetostatic surface waves in the dipole-exchange regime.",1311.0676v1
+2013-11-13,Thermally activated in-plane magnetization rotation induced by spin torque,"We study the role of thermal fluctuations on the spin dynamics of a thin
+permalloy film with a focus on the behavior of spin torque and find that the
+thermally assisted spin torque results in new aspects of the magnetization
+dynamics. In particular, we uncover the formation of a finite, spin
+torque-induced, in-plane magnetization component. The orientation of the
+in-plane magnetization vector depends on the temperature and the spin-torque
+coupling. We investigate and illustrate that the variation of the temperature
+leads to a thermally-induced rotation of the in-plane magnetization.",1311.3120v1
+2013-11-30,Fabrication and characterisation of nanospintronic devices,"We report an improved fabrication scheme for carbon based nanospintronic
+devices and demonstrate the necessity for a careful data analysis to
+investigate the fundamental physical mechanisms leading to magnetoresistance.
+The processing with a low-density polymer and an optimised recipe allows us to
+improve the electrical, magnetic and structural quality of ferromagnetic
+Permalloy contacts on lateral carbon nanotube (CNT) quantum dot spin valve
+devices, with comparable results for thermal and sputter deposition of the
+material. We show that spintronic nanostructures require an extended data
+analysis, since the magnetisation can affect all characteristic parameters of
+the conductance features and lead to seemingly anomalous spin transport. In
+addition, we report measurements on CNT quantum dot spin valves that seem not
+to be compatible with the orthodox theories for spin transport in such
+structures.",1312.0159v1
+2013-12-05,Strong impact of the eddy-current shielding on ferromagnetic resonance response of sub-skin-depth-thick conducting magnetic multilayers,"Exchange-coupled nonmagnetic (NM) and ferromagnetic (FM) conducting
+multilayers are crucial for microwave spintronic devices of the future. We
+demonstrate, experimentally and theoretically, that in broadband measurements
+of ferromagnetic resonance (FMR) 10-70 nm-thick permalloy (Py) layers are
+shielded from the dynamic magnetic field of the microstrip line by eddy
+currents circulating in the NM capping layers, which strongly diminishes the
+amplitude of magnetisation precession in the FM material. Our findings have
+direct implications for designing broadband FMR and measurements of spin
+current injection through interfaces realised by placing a conducting
+multilayer above a microwave microstrip line. We show that the eddy-current
+shielding is very strong at high microwave frequencies (30 GHz) even when the
+thickness of the NM capping layer is <5 nm, which is well below the microwave
+skin depth for Au, Cu, Ta, Pd, Pt and other NM metals technologically important
+for spintronics.",1312.1404v2
+2013-12-17,Manipulating domain wall chirality by current pulses in Permalloy/Ir nanostrips,"Using magnetic force microscopy and micromagnetic simulations, we studied the
+effect of Oersted magnetic fields on the chirality of transverse magnetic
+domain walls in Fe$_{20}$Ni$_{80}$/Ir bilayer nanostrips. Applying nanosecond
+current pulses with a current density of around $2\times10^{12}$ A/m$^2$, the
+chirality of a transverse domain wall could be switched reversibly and
+reproducibly. These current densities are similar to the ones used for
+current-induced domain wall motion, indicating that the Oersted field may
+stabilize the transverse wall chirality during current pulses and prevent
+domain wall transformations.",1312.4918v1
+2014-01-22,Current-induced magnetization dynamics at the edge of a two-dimensional electron system with strong spin-orbit coupling,"We experimentally investigate electron transport through the interface
+between a permalloy ferromagnet and the edge of a two-dimensional electron
+system with strong Rashba-type spin-orbit coupling. We observe strongly
+non-linear transport around zero bias at millikelvin temperatures. The observed
+nonlinearity is fully suppressed above some critical values of temperature,
+magnetic field, and current through the interface. We interpret this behavior
+as the result of spin accumulation at the interface and its current-induced
+absorption as a magnetization torque.",1401.5719v2
+2014-04-03,Enhanced DC Spin Pumping into a Fluctuating Ferromagnet near Tc,"A linear-response formulation of the dc spin pumping, i.e., a spin injection
+from a precessing ferromagnet into an adjacent spin sink, is developed in view
+of describing many-body effects caused by spin fluctuations in the spin sink.
+It is shown that, when an itinerant ferromagnet near Tc is used as the spin
+sink, the spin pumping is largely increased owing to the fluctuation
+enhancement of the spin conductance across the precessing ferromagnet/spin sink
+interface. As an example, the enhanced spin pumping from permalloy into nickel
+palladium alloy (Tc ~ 20K) is analyzed by means of a self-consistent
+renormalization scheme, and it is predicted that the enhancement can be as
+large as tenfold.",1404.0768v2
+2014-04-03,Anomalously Weak Cooper Pair-breaking by Exchange Energy in Ferromagnet/Superconductor Bilayers,"We report the superconducting transition temperature $T_c$ vs. thickness
+$d_F$ of Ferromagnet/Superconductor (F/S) bilayers, where F is a strong $3d$
+ferromagnet (Ni, Ni$_{0.81}$Fe$_{0.19}$ (Permalloy), Co$_{0.5}$Fe$_{0.5}$) and
+S = Nb, taken from superfluid density measurements rather than resistivity. By
+regrouping the many physical parameters that appear in theory, we show that the
+effective exchange energy is determined from the F film thickness $d_F$ where
+$T_c$ vs. $d_F$ begins to flatten out. Using this rearranged theory we
+conclude: 1) the effective exchange energy, $E_{ex}$, is about 15 times smaller
+than measured by ARPES and 5 times smaller than deduced in previous studies
+similar to ours; 2) the dirty-limit coherence length, $\xi_{F}$, for Cooper
+pairs in F is larger than the electron mean free path, $\ell_F$; and 3) the
+$3d$-F/Nb interface is enough of a barrier that Cooper pairs typically must hit
+it several times before getting through. The Py/Nb and CoFe/Nb interfaces are
+more transparent than the Ni/Nb interface.",1404.1032v1
+2014-04-04,Observation of inverse spin Hall effect in bismuth selenide,"Bismuth Selenide (Bi2Se3) is a topological insulator exhibiting helical spin
+polarization and strong spin-orbit coupling. The spin-orbit coupling links the
+charge current to spin current via the spin Hall effect (SHE). We demonstrate a
+Bi2Se3 spin detector by injecting the pure spin current from a magnetic
+permalloy layer to a Bi2Se3 thin film and detect the inverse SHE in Bi2Se3. The
+spin Hall angle of Bi2Se3 is found to be 0.0093 and the spin diffusion length
+in Bi2Se3 to be 6.2 nm at room temperature. Our results suggest that
+topological insulators with strong spin-orbit coupling can be used in
+functional spintronic devices.",1404.1146v2
+2014-09-04,Detection of the dc inverse spin Hall effect due to spin pumping in a novel meander-stripline geometry,"The dc voltage obtained from the inverse spin Hall effect (iSHE) due to spin
+pumping in ferromagnet/normal-metal (NM) bilayers can be unintentionally
+superimposed with magnetoresistive rectification of ac charge currents in the
+ferromagnetic layer. We introduce a geometry in which these spurious
+rectification voltages vanish while the iSHE voltage is maximized. In this
+geometry, a quantitative study of the dc iSHE is performed in a broad frequency
+range for Permalloy/NM multilayers with NM={Pt, Ta, Cu/Au, Cu/Pt}. The
+experimentally recorded voltages can be fully ascribed to the iSHE due to spin
+pumping. Furthermore we measure a small iSHE voltage in single CoFe thin films.",1409.1290v1
+2014-09-30,Origin of inverse Rashba-Edelstein effect at Cu/Bi interface using lateral spin valves,"The spin transport and spin-to-charge current conversion properties of
+bismuth are investigated using permalloy/copper/bismuth (Py/Cu/Bi)lateral spin
+valve structures. The spin current is strongly absorbed at the surface of Bi,
+leading to ultra-short spin diffusion lengths. A spin-to-charge current
+conversion is measured, which is attributed to the inverse Rashba-Edelstein
+effect at the Cu/Bi interface. The spin-current-induced charge current is found
+to change direction with increasing temperature. A theoretical analysis relates
+this behavior to the complex spin structure and dispersion of the surface
+states at the Fermi energy. The understanding of this phenomenon opens novel
+possibilities to exploit spin-orbit coupling to create, manipulate, and detect
+spin currents in 2D systems.",1409.8540v2
+2014-10-24,Rectification of radio frequency current in giant magnetoresistance spin valve,"We report on a highly efficient spin diode effect in an exchange-biased
+spin-valve giant magnetoresistance (GMR) strips. In such multilayer structures,
+symmetry of the current distribution along the vertical direction is broken
+and, as a result, a non-compensated Oersted field acting on the magnetic free
+layer appears. This field, in turn, is a driving force of magnetization
+precessions. Due to the GMR effect, resistance of the strip oscillates
+following the magnetization dynamics. This leads to rectification of the
+applied radio frequency current and induces a direct current voltage $V_{DC}$.
+We present a theoretical description of this phenomenon and calculate the spin
+diode signal, $V_{DC}$, as a function of frequency, external magnetic field,
+and angle at which the external field is applied. A satisfactory quantitative
+agreement between theoretical predictions and experimental data has been
+achieved. Finally, we show that the spin diode signal in GMR devices is
+significantly stronger than in the anisotropic magnetoresistance
+permalloy-based devices.",1410.6672v1
+2015-01-12,Direct Imaging of Complex Spin Ice Behavior and Ordered Sublattices in Artificial Ferromagnetic Quasicrystals,"We have imaged magnetization textures of permalloy films patterned into
+Penrose P2 tilings (P2T) using scanning electron microscopy with polarization
+analysis (SEMPA). P2T film segments have near-uniform, bipolar magnetization,
+similar to artificial spin ices, but with asymmetric vertex coordination that
+induces a more complex spin ice behavior mediated by exchange interactions in
+vertex domain walls. Numerical simulations including long-range dipole
+interactions agree with SEMPA images of as-grown P2T, and predict a
+ferromagnetic ground state for a 2D P2T lattice of classical Ising spins.",1501.02760v1
+2015-02-22,Spin-valve Effect in NiFe/MoS2/NiFe Junctions,"Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have
+been recently proposed as appealing candidate materials for spintronic
+applications owing to their distinctive atomic crystal structure and exotic
+physical properties arising from the large bonding anisotropy. Here we
+introduce the first MoS2-based spin-valves that employ monolayer MoS2 as the
+nonmagnetic spacer. In contrast with what expected from the semiconducting
+band-structure of MoS2, the vertically sandwiched-MoS2 layers exhibit metallic
+behavior. This originates from their strong hybridization with the Ni and Fe
+atoms of the Permalloy (Py) electrode. The spin-valve effect is observed up to
+240 K, with the highest magnetoresistance (MR) up to 0.73% at low temperatures.
+The experimental work is accompanied by the first principle electron transport
+calculations, which reveal an MR of ~ 9% for an ideal Py/MoS2/Py junction. Our
+results clearly identify TMDs as a promising spacer compound in magnetic tunnel
+junctions and may open a new avenue for the TMDs-based spintronic applications.",1502.06154v2
+2015-03-30,Suppression of Spin Pumping Between Ni$_{80}$Fe$_{20}$ and Cu by a Graphene Interlayer,"We compare ferromagnetic resonance measurements of Permalloy
+Ni$_{80}$Fe$_{20}$ (Py) films sputtered onto Cu(111) films with and without a
+graphene (Gr) interlayer grown by chemical vapor deposition before Py
+deposition. A two-angle sputtering method ensured that neither Gr nor Py was
+degraded by the sample preparation process. We find the expected damping
+enhancement from spin pumping for the Py/Cu case and no detectable enhancement
+for the Py/Gr/Cu case. Since damping is sensitive to effects other than spin
+pumping, we used magnetometry to verify that differences in Py magnetostatic
+properties are not responsible for the difference in damping. We attribute the
+suppression of spin pumping in Py/Gr/Cu to the large contact resistance of the
+Gr/Cu interface.",1503.08777v1
+2015-04-01,Multiscale modeling of ultrafast element-specific magnetization dynamics of ferromagnetic alloys,"A hierarchical multiscale approach to model the magnetization dynamics of
+ferromagnetic ran- dom alloys is presented. First-principles calculations of
+the Heisenberg exchange integrals are linked to atomistic spin models based
+upon the stochastic Landau-Lifshitz-Gilbert (LLG) equation to calculate
+temperature-dependent parameters (e.g., effective exchange interactions,
+damping param- eters). These parameters are subsequently used in the
+Landau-Lifshitz-Bloch (LLB) model for multi-sublattice magnets to calculate
+numerically and analytically the ultrafast demagnetization times. The developed
+multiscale method is applied here to FeNi (permalloy) as well as to copper-
+doped FeNi alloys. We find that after an ultrafast heat pulse the Ni sublattice
+demagnetizes faster than the Fe sublattice for the here-studied FeNi-based
+alloys.",1504.00199v1
+2015-05-18,Evidence on the macroscopic length scale spin coherence for the edge currents in a narrow HgTe quantum well,"We experimentally investigate spin-polarized electron transport between two
+ferromagnetic contacts, placed at the edge of a two-dimensional electron system
+with band inversion. The system is realized in a narrow (8~nm) HgTe quantum
+well, the ferromagnetic side contacts are formed from a pre-magnetized
+permalloy film. In zero magnetic field, we find a significant edge current
+contribution to the transport between two ferromagnetic contacts. We
+experimentally demonstrate that this transport is sensitive to the mutual
+orientation of the magnetization directions of two 200~$\mu$m-spaced
+ferromagnetic leads. This is a direct experimental evidence on the
+spin-coherent edge transport over the macroscopic distances. Thus, the spin is
+extremely robust at the edge of a two-dimensional electron system with band
+inversion, confirming the helical spin-resolved nature of edge currents.",1505.04535v1
+2015-08-03,Static magnetic proximity effect in Pt/Ni$_{1-x}$Fe$_x$ bilayers investigated by x-ray resonant magnetic reflectivity,"We present x-ray resonant magnetic reflectivity (XRMR) as a very sensitive
+tool to detect proximity induced interface spin polarization in Pt/Fe,
+Pt/Ni$_{33}$Fe$_{67}$, Pt/Ni$_{81}$Fe$_{19}$ (permalloy), and Pt/Ni bilayers.
+We demonstrate that a detailed analysis of the reflected x-ray intensity gives
+insight in the spatial distribution of the spin polarization of a non-magnetic
+metal across the interface to a ferromagnetic layer. The evaluation of the
+experimental results with simulations based on optical data from ab initio
+calculations provides the induced magnetic moment per Pt atom in the spin
+polarized volume adjacent to the ferromagnet. We find the largest spin
+polarization in Pt/Fe and a much smaller magnetic proximity effect in Pt/Ni.
+Additional XRMR experiments with varying photon energy are in good agreement
+with the theoretical predictions for the energy dependence of the magnetooptic
+parameters and allow identifying the optical dispersion $\delta$ and absorption
+$\beta$ across the Pt L3-absorption edge.",1508.00379v1
+2015-08-06,Interface-driven spin-torque ferromagnetic resonance by Rashba coupling at the interface between non-magnetic materials,"The Rashba-Edelstein effect stems from the interaction between the electron's
+spin and its momentum induced by spin-orbit interaction at an interface or a
+surface. It was shown that the inverse Rashba-Edelstein effect can be used to
+convert a spin- into a charge current. Here, we demonstrate that a Bi/Ag Rashba
+interface can even drive an adjacent ferromagnet to resonance. We employ a
+spin-torque ferromagnetic resonance excitation/detection scheme which was
+developed originally for a bulk spin-orbital effect, the spin Hall effect. In
+our experiment, the direct Rashba-Edelstein effect generates an oscillating
+spin current from an alternating charge current driving the magnetization
+precession in a neighboring permalloy (Py, Ni80Fe20) layer. Electrical
+detection of the magnetization dynamics is achieved by a rectification
+mechanism of the time dependent multilayer resistance arising from the
+anisotropic magnetoresistance.",1508.01410v1
+2015-09-03,All-Optical Vector Measurement of Spin-Orbit-Induced Torques Using Both Polar and Quadratic Magneto-Optic Kerr Effects,"We demonstrate that the magneto-optic-Kerr effect with normal light incidence
+can be used to obtain quantitative optical measurements of both components of
+spin-orbit-induced torque (both the antidamping and effective-field components)
+in heavy-metal/ferromagnet bilayers. This is achieved by analyzing the
+quadratic Kerr effect as well as the polar Kerr effect. The two effects can be
+distinguished by properly selecting the polarization of the incident light. We
+use this all-optical technique to determine the spin-orbit torques generated by
+a series of Pt/Permalloy samples, finding values in excellent agreement with
+spin-torque ferromagnetic resonance measurements.",1509.01266v1
+2015-09-10,Role of hexagonal boron nitride in protecting ferromagnetic nanostructures from oxidation,"Ferromagnetic contacts are widely used to inject spin polarized currents into
+non-magnetic materials such as semiconductors or 2-dimensional materials like
+graphene. In these systems, oxidation of the ferromagnetic materials poses an
+intrinsic limitation on device performance. Here we investigate the role of
+ex-situ transferred chemical vapour deposited hexagonal boron nitride (hBN) as
+an oxidation barrier for nanostructured cobalt and permalloy electrodes. The
+chemical state of the ferromagnets was investigated using X-ray photoemission
+electron microscopy owing to its high sensitivity and lateral resolution. We
+have compared the oxide thickness formed on ferromagnetic nanostructures
+covered by hBN to uncovered reference structures. Our results show that hBN
+reduces the oxidation rate of ferromagnetic nanostructures suggesting that it
+could be used as an ultra-thin protection layer in future spintronic devices.",1509.03087v2
+2015-12-15,Moderate Positive Spin Hall Angle in Uranium,"We report measurements of spin pumping and the inverse spin Hall effect in
+Ni80Fe20/Uranium bilayers designed to study the efficiency of spin-charge
+interconversion in a super-heavy element. We employ broad-band ferromagnetic
+resonance on extended films to inject a spin current from the Ni80Fe20
+(permalloy) into the uranium layer, which is then converted into an electric
+field by the inverse spin Hall effect. Surprisingly, our results suggest a spin
+mixing conductance of order 2x10 e19 m-2 and a positive spin Hall angle of
+0.004, which are both merely comparable to those of several transition metals.
+These results thus support the idea that the electronic configuration may be at
+least as important as the atomic number in governing spin pumping across
+interfaces and subsequent spin Hall effects. In fact, given that both the
+magnitude and the sign are unexpected based on trends in d-electron systems,
+materials with unfilled f-electron orbitals may hold additional exploration
+avenues for spin physics.",1512.04903v1
+2016-01-21,Vortex Dynamics-Mediated Low-Field Magnetization Switching in an Exchange-Coupled System,"A magnetic vortex has attracted significant attention since it is a
+topologically stable magnetic structure in a soft magnetic nanodisk. Many
+studies have been devoted to understanding the nature of magnetic vortex in
+isolated systems. Here we show a new aspect of a magnetic vortex the dynamics
+of which strongly affects the magnetic structures of environment. We exploit a
+nanodot of an exchange-coupled bilayer with a soft magnetic Ni81Fe19
+(permalloy; Py) having a magnetic vortex and a perpendicularly magnetized
+L10-FePt exhibiting a large switching field (Hsw). The vortex dynamics with
+azimuthal spin waves makes the excess energy accumulate in the Py, which
+triggers the reversed-domain nucleation in the L10-FePt at a low magnetic
+field. Our results shed light on the non-local mechanism of a reversed-domain
+nucleation, and provide with a route for efficient Hsw reduction that is needed
+for ultralow-power spintronic devices.",1601.05521v1
+2016-01-27,Quantification of a propagating spin-wave-packet created by an ultrashort laser pulse in a thin film of magnetic metal,"Coherent spin-wave generation by focused ultrashort laser pulse irradiation
+was investigated for a permalloy thin film at micrometer scale using an
+all-optical space and time-resolved magneto-optical Kerr effect. The spin-wave
+packet propagating perpendicular to magnetization direction was clearly
+observed, however that propagating parallel to the magnetization direction was
+not observed. The propagation length, group velocity, center frequency, and
+packet-width of the observed spin-wave packet were evaluated and quantitatively
+explained in terms of the propagation of a magneto-static spin-wave driven by
+ultrafast change of an out-of-plane demagnetization field induced by the
+focused-pulse laser.",1601.07247v1
+2016-01-28,Spin-Cherenkov effect in a magnetic nanostrip with interfacial Dzyaloshinskii-Moriya interaction,"Spin-Cherenkov effect enables strong excitations of spin waves (SWs) with
+nonlinear wave dispersions. The Dzyaloshinskii-Moriya interaction (DMI) results
+in anisotropy and nonreciprocity of SWs propagation. In this work, we study the
+effect of the interfacial DMI on SW Cherenkov excitations in permalloy
+thin-film strips within the framework of micromagnetism. By performing
+micromagnetic simulations, it is shown that coherent SWs are excited when the
+velocity of a moving magnetic source exceeds the propagation velocity of the
+SWs. Moreover, the threshold velocity of the moving magnetic source with finite
+DMI can be reduced compared to the case of zero DMI. It thereby provides a
+promising route towards efficient SW generation and propagation, with potential
+applications in spintronic and magnonic devices.",1601.07755v2
+2016-02-11,Thermal spin injection and interface insensitivity in permalloy/aluminum metallic non-local spin valves,"We present measurements of thermal and electrical spin injection in nanoscale
+metallic non-local spin valve (NLSV) structures. Informed by measurements of
+the Seebeck coefficient and thermal conductivity of representative films made
+using a micromachined Si-N thermal isolation platform, we use simple analytical
+and finite element thermal models to determine limits on the thermal gradient
+driving thermal spin injection and calculate the spin dependent Seebeck
+coefficient to be $-0.5\ \mu\mathrm{V}/\mathrm{K}< S_{s}<-1.3\
+\mu\mathrm{V}/\mathrm{K}$. This is comparable in terms of the fraction of the
+absolute Seebeck coefficient to previous results, despite dramatically smaller
+electrical spin injection signals. Since the small electrical spin signals are
+likely caused by interfacial effects, we conclude that thermal spin injection
+is less sensitive to the FM/NM interface, and possibly benefits from a layer of
+oxidized ferromagnet, which further stimulates interest in thermal spin
+injection for applications in sensors and pure spin current sources.",1602.03859v2
+2016-04-02,Influence of Joule heating on current-induced domain wall depinning,"The domain wall depinning from a notch in a Permalloy nanostrip on top of a
+${\rm SiO_2/Si}$ substrate is studied theoretically under application of static
+magnetic fields and the injection of short current pulses. The influence of
+Joule heating on current-induced domain wall depinning is explored
+self-consistently by coupling the magnetization dynamics in the ferromagnetic
+strip to the heat transport throughout the system. Our results indicate that
+Joule heating plays a remarkable role in these processes, resulting in a
+reduction in the critical depinning field and/or in a temporary destruction of
+the ferromagnetic order for typically injected current pulses. In agreement
+with experimental observations, similar pinning-depinning phase diagrams can be
+deduced for both current polarities when the Joule heating is taken into
+account. These observations, which are incompatible with the sole contribution
+of spin transfer torques, provide a deeper understanding of the physics
+underlying these processes and establish the real scope of the spin transfer
+torque. They are also relevant for technological applications based on
+current-induced domain-wall motion along soft strips.",1604.00522v2
+2016-04-15,Chaotic dynamics of magnetic domain walls in nanowires,"The nonlinear dynamics of a transverse domain wall (TDW) in Permalloy and
+Nickel nanostrips with two artificially patterned pinning centers is studied
+numerically up to rf frequencies. The phase diagram frequency - driving
+amplitude shows a rich variety of dynamical behaviors depending on the material
+parameters and the type and shape of pinning centers. We find that T-shaped
+traps (antinotches) create a classical double well Duffing potential that leads
+to a small chaotic region in the case of Nickel and a large one for Py. In
+contrast, the rectangular constrictions (notches) create an exponential
+potential that leads to larger chaotic regions interspersed with periodic
+windows for both Py and Ni. The influence of temperature manifests itself by
+enlarging the chaotic region and activating thermal jumps between the pinning
+sites while reducing the depinning field at low frequency in the notched
+strips.",1604.04438v1
+2016-04-16,A broadband Ferromagnetic Resonance dipper probe for magnetic damping measurements from 4.2 K to 300 K,"A dipper probe for broadband Ferromagnetic Resonance (FMR) operating from 4.2
+K to room temperature is described. The apparatus is based on a 2-port
+transmitted microwave signal measurement with a grounded coplanar waveguide.
+The waveguide generates a microwave field and records the sample response. A
+3-stage dipper design is adopted for fast and stable temperature control. The
+temperature variation due to FMR is in the milli-Kelvin range at liquid helium
+temperature. We also designed a novel FMR probe head with a spring-loaded
+sample holder. Improved signal-to-noise ratio and stability compared to a
+common FMR head are achieved. Using a superconducting vector magnet we
+demonstrate Gilbert damping measurements on two thin film samples using a
+vector network analyzer with frequency up to 26 GHz: 1) A Permalloy film of 5
+nm thickness and 2) a CoFeB film of 1.5 nm thickness. Experiments were
+performed with the applied magnetic field parallel and perpendicular to the
+film plane.",1604.04688v1
+2016-04-22,Nanoscale control of heat and spin conductance in artificial spin chains,"We describe a mechanism to control energy and magnetisation currents in an
+artificial spin-chain, consisting of an array of Permalloy nano-disks coupled
+through the magneto-dipolar interaction. The chain is kept out of equilibrium
+by two thermal baths with different temperatures connected to its ends, which
+control the current propagation. Transport is enhanced by applying a uniform
+radio frequency pump field resonating with some of the spin-wave modes of the
+chain. Moreover, the two currents can be controlled independently by tuning the
+static field applied on the chain. Thus we describe two effective means for the
+independent control of coupled currents and the enhancement of thermal and
+spin-wave conductivity in a realistic magnonics device, suggesting that similar
+effects could be observed in a large class of nonlinear oscillating systems.",1604.06572v3
+2016-05-10,Nanocavity optomechanical torque magnetometry and radiofrequency susceptometry,"Nanophotonic optomechanical devices allow observation of nanoscale vibrations
+with sensitivity that has dramatically advanced metrology of nanomechanical
+structures [1-9] and has the potential to impact studies of nanoscale physical
+systems in a similar manner [10, 11]. Here we demonstrate this potential with a
+nanophotonic optomechanical torque magnetometer and radiofrequency (RF)
+magnetic susceptometer. Exquisite readout sensitivity provided by a nanocavity
+integrated within a torsional nanomechanical resonator enables observations of
+the unique net magnetization and RF-driven responses of single mesoscopic
+magnetic structures in ambient conditions. The magnetic moment resolution is
+sufficient for observation of Barkhausen steps in the magnetic hysteresis of a
+lithographically patterned permalloy island [12]. In addition, significantly
+enhanced RF susceptibility is found over narrow field ranges and attributed to
+thermally assisted driven hopping of a magnetic vortex core between neighboring
+pinning sites [13]. The on-chip magneto-susceptometer scheme offers a promising
+path to powerful integrated cavity optomechanical devices for quantitative
+characterization of magnetic micro- and nanosystems in science and technology.",1605.03138v2
+2016-06-03,Crystal Structure Manipulation of the Exchange Bias in an Antiferromagnetic Film,"Exchange bias is one of the most extensively studied phenomena in magnetism,
+since it exerts a unidirectional anisotropy to a ferromagnet (FM) when coupled
+to an antiferromagnet (AFM) and the control of the exchange bias is therefore
+very important for technological applications, such as magnetic random access
+memory and giant magnetoresistance sensors. In this letter, we report the
+crystal structure manipulation of the exchange bias in epitaxial hcp Cr2O3
+films. By epitaxially growing twined (10-10) oriented Cr2O3 thin films, of
+which the c axis and spins of the Cr atoms lie in the film plane, we
+demonstrate that the exchange bias between Cr2O3 and an adjacent permalloy
+layer is tuned to in-plane from out-of-plane that has been observed in (0001)
+oriented Cr2O3 films. This is owing to the collinear exchange coupling between
+the spins of the Cr atoms and the adjacent FM layer. Such a highly anisotropic
+exchange bias phenomenon is not possible in polycrystalline films.",1606.01086v1
+2016-06-09,Snell's Law for Spin Waves,"We report the experimental observation of Snell's law for magneto-static spin
+waves in thin ferromagnetic Permalloy films by imaging incident, refracted and
+reflected waves. We use a thickness step as the interface between two media
+with different dispersion relation. Since the dispersion relation for
+magneto-static waves in thin ferromagnetic films is anisotropic, deviations
+from the isotropic Snell's law known in optics are observed for incidence
+angles larger than 25\textdegree{} with respect to the interface normal between
+the two magnetic media. Furthermore, we can show that the thickness step
+modifies the wavelength and the amplitude of the incident waves. Our findings
+open up a new way of spin wave steering for magnonic applications.",1606.02895v1
+2016-09-20,Positive Exchange Bias between Permalloy and Twined (10-10)-Cr2O3 Films,"We report the discovery of a positive exchange bias between Ni80Fe20 (Py) and
+twined (10-10)-Cr2O3 film near its blocking temperature (TB) when it is cooled
+in an in-plane magnetic field applied along 45 degrees from the two spin
+configurations of the Cr atoms. This is an abnormal behavior compared to the
+negative exchange bias at all temperatures below TB when the cooling and
+measuring magnetic fields are applied along one of the two spin configurations
+of the Cr atoms. We speculate these results could be related to the exchange
+interactions between the twined structure of the (10-10)-Cr2O3 film epitaxially
+grown on the rutile (001)-TiO2 substrate.",1609.06216v1
+2016-10-14,Electric-field tunable spin waves in PMN-PT/NiFe heterostructure: experiment and micromagnetic simulations,"We present a comprehensive theoretical and experimental study of
+voltage-controlled standing spin waves resonance (SSWR) in PMN-PT/NiFe
+multiferroic heterostructures patterned into microstrips. A spin-diode
+technique was used to observe ferromagnetic resonance (FMR) mode and SSWR in
+NiFe strip mechanically coupled with a piezoelectric substrate. Application of
+an electric field to a PMNPT creates a strain in permalloy and thus shifts the
+FMR and SSWR fields due to the magnetostriction effect. The experimental
+results are compared with micromagnetic simulations and a good agreement
+between them is found for dynamics of FMR and SSWR with and without electric
+field. Moreover, micromagnetic simulations enable us to discuss the amplitude
+and phase spatial distributions of FMR and SSWR modes, which are not directly
+observable by means of spin diode detection technique.",1610.04500v1
+2016-11-09,Effect of nanostructure layout on spin pumping phenomena in antiferromagnet/ nonmagnetic metal/ ferromagnet multilayered stacks,"In this work we focus on magnetic relaxation in Mn$_{80}$Ir$_{20}$(12 nm)/
+Cu(6 nm)/ Py($d_\mathrm{F}$) antiferromagnet/Cu/ferromagnet (AFM/Cu/FM)
+multilayers with different thickness of the ferromagnetic permalloy layer. An
+effective FM-AFM interaction mediated via the conduction electrons in the
+nonmagnetic Cu spacer -- the spin-pumping effect -- is detected as an increase
+in the linewidth of the ferromagnetic resonance (FMR) spectra and a shift of
+the resonant magnetic field. We further find experimentally that the
+spin-pumping-induced contribution to the linewidth is inversely proportional to
+the thickness of the Py layer. We show that this thickness dependence likely
+originates from the dissipative dynamics of the free and localized spins in the
+AFM layer. The results obtained could be used for tailoring the dissipative
+properties of spintronic devices incorporating antiferromagnetic layers.",1611.02865v1
+2017-01-19,Understanding magnetotransport signatures in networks of connected permalloy nanowires,"The change in electrical resistance associated with the application of an
+external magnetic field is known as the magnetoresistance (MR). The measured MR
+is quite complex in the class of connected networks of single-domain
+ferromagnetic nanowires, known as ""artificial spin ice"", due to the
+geometrically-induced collective behavior of the nanowire moments. We have
+conducted a thorough experimental study of the MR of a connected honeycomb
+artificial spin ice, and we present a simulation methodology for understanding
+the detailed behavior of this complex correlated magnetic system. Our results
+demonstrate that the behavior, even at low magnetic fields, can be
+well-described only by including significant contributions from the vertices at
+which the legs meet, opening the door to new geometrically-induced MR
+phenomena.",1701.05618v1
+2017-01-30,Magnetic diode at $T$ = 300 K,"We report the finding of unidirectional electronic properties, analogous to a
+semiconductor diode, in two-dimensional artificial permalloy honeycomb lattice
+of ultra-small bond, with a typical length of ~ 12 nm. The unidirectional
+transport behavior, characterized by the asymmetric colossal enhancement in
+differential conductivity at a modest current application of ~ 10-15 $\mu$A,
+persists to T = 300 K in honeycomb lattice of thickness ~ 6 nm. The asymmetric
+behavior arises without the application of magnetic field. A qualitative
+analysis of experimental data suggests the role of magnetic charge or monopoles
+in the unusual observations with strong implication for spintronics.",1701.08455v3
+2017-07-25,3D MOKE spin-orbit torque magnetometer,"We demonstrate simultaneous detection of current driven antidamping-like and
+field-like spin-orbit torques in heavy metal/ferromagnetic metal bilayers by
+measuring all three magnetization components m_(x,) m_y, and m_z using the
+vector magneto-optic Kerr effect. We have also implemented a self-calibration
+method to accurately determine the effective fields of spin-orbit torques. With
+this technique, we investigate the magnitude and direction of spin-orbit
+torques in a series of platinum/permalloy samples. The values found are in
+excellent agreement with results obtained via quadratic magneto-optic Kerr
+effect, planar Hall effect, and spin transfer ferromagnetic resonance
+measurements.",1707.08565v1
+2017-11-23,Effect of Notch Structure on Magnetic Domain Movement in Planar Nanowires,"We present the direct observation of magnetic domain motion in permalloy
+nanowires with notches using a wide-field Kerr microscopy technique. The domain
+wall motion can be modulated by the size and shape of the notch structure in
+the nanowires. It is demonstrated that the coercive fields can be tuned by
+modulating the notches. The experimental results are consistent with the
+micro-magnetic simulation results. The relationship between the notch angle and
+the domain nuclease are also studied. This work is useful for the design and
+development of the notch-based spintronic devices.",1711.08788v1
+2017-11-28,Transmission x-ray microscopy at low temperatures - analyzing supercurrents with high spatial resolution,"Scanning transmission x-ray microscopy has been used to image electric
+currents in superconducting films at temperatures down to 20 K. The magnetic
+stray field of supercurrents in a thin YBaCuO film is mapped into a
+soft-magnetic coating of permalloy. The so created local magnetization of the
+ferromagnetic film can be detected by dichroic absorption of polarized x-rays.
+To enable high-quality measurements in transmission geometry the whole
+heterostructure of ferromagnet, superconductor and single-crystalline substrate
+has been thinned to an overall thickness of less than 1 micron. With this novel
+technique local supercurrents can be analyzed in a wide range of temperatures
+and magnetic fields. A magnetic resolution of less than 100nm together with
+simultaneously obtained nanostructural data allow the correlation of local
+supercurrents with the micro- and nanostructure of the superconducting film.",1711.10230v1
+2018-05-21,"11,11,12,12-tetracyanonaphtho-2,6-quinodimethane in Contact with Ferromagnetic Electrodes for Organic Spintronics","Spinterface engineering has shown quite important roles in organic
+spintronics as it can improve spin injection or extraction. In this study,
+11,11,12,12-tetracyanonaptho-2,6-quinodimethane (TNAP) is introduced as an
+interfacial layer for a prototype interface of Fe/TNAP. We report an
+element-specific investigation of the electronic and magnetic structures of
+Fe/TNAP system by use of near edge X-Ray absorption fine structure (NEXAFS) and
+X-ray magnetic circular dichroism (XMCD). Strong hybridization between TNAP and
+Fe and induced magnetization of N atoms in TNAP molecule are observed. XMCD sum
+rule analysis demonstrates that the adsorption of TNAP reduces the spin moment
+of Fe by 12%. In addition, induced magnetization in N K-edge of TNAP has also
+been found with other commonly used ferromagnets in organic spintronics, such
+as La0.7Sr0.3MnO3 and permalloy, which makes TNAP a very promising molecule for
+spinterface engineering in organic spintronics.",1805.07906v1
+2018-05-25,"Calculating the transport properties of magnetic materials from first-principles including thermal and alloy disorder, non-collinearity and spin-orbit coupling","A density functional theory based two-terminal scattering formalism that
+includes spin-orbit coupling and spin non-collinearity is described. An
+implementation using tight-binding muffin-tin orbitals combined with extensive
+use of sparse matrix techniques allows a wide variety of inhomogeneous
+structures to be flexibly modelled with various types of disorder including
+temperature induced lattice and spin disorder. The methodology is illustrated
+with calculations of the temperature dependent resistivity and magnetization
+damping for the important substitutional disordered magnetic alloy Permalloy
+(Py), Ni$_{80}$Fe$_{20}$. Comparison of calculated results with recent
+experimental measurements of the damping (including its temperature dependence)
+indicates that the scattering approach captures the most important
+contributions to this important property.",1805.10062v1
+2018-06-12,Asymmetric motion of magnetically actuated artificial cilia,"Most microorganisms use hair-like cilia with asymmetric beating to perform
+vital bio-physical processes. In this paper, we demonstrate a novel fabrication
+method for creating magnetic artificial cilia capable of such biologically
+inspired asymmetrical beating pattern essential for creating microfluidic
+transport in low Reynolds number. The cilia are fabricated using a lithographic
+process in conjunction with deposition of magnetic nickel-iron permalloy to
+create flexible filaments that can be manipulated by varying an external
+magnetic field. A rotating permanent magnet is used to actuate the cilia. We
+examine the kinematics of a cilium and demonstrate that the cilium motion is
+defined by an interplay among elastic, magnetic, and viscous forces.
+Specifically, the forward stroke is induced by the rotation of the magnet which
+bends the cilium, whereas the recovery stroke is defined by the straightening
+of the deformed cilium, releasing the accumulated elastic potential energy.
+This difference in dominating forces acting during the forward stroke and the
+recovery stroke leads to an asymmetrical beating pattern of the cilium. Such
+magnetic cilia can find applications in microfluidic pumping, mixing, and other
+fluid handling processes.",1806.04320v1
+2018-06-15,Design of a CubeSat Payload to Test a Magnetic Measurement System for Space-borne Gravitational Wave Detectors,"Space observatories for gravitational radiation such as LISA are equipped
+with dedicated on-board instrumentation capable of measuring magnetic fields
+with low-noise conditions at millihertz frequencies. The reason is that the
+core scientific payload can only operate successfully if the magnetic
+environment meets certain strict low-frequency requirements. With this purpose,
+a simplified version of the proposed magnetic measurement system for LISA has
+been developed for a six-unit CubeSat, which will make it possible to improve
+the technology readiness level (TRL) of the instrument. The special feature of
+the experiment is that the magnetic sensors integrated in the payload are
+magnetically shielded to low-frequency fluctuations by using a small
+cylindrical permalloy enclosure. This will allow the in-flight noise
+characterization of the system under the CubeSat orbit environment. Therefore,
+a CubeSat platform will offer the opportunity to measure the capability of the
+instrument and will guide the progress towards the improved magnetic
+measurement system for LISA. This article describes the principal
+characteristics and implementation of the CubeSat payload.",1806.05913v1
+2018-06-25,Wideband and on-chip excitation for dynamical spin injection into graphene,"Graphene is an ideal material for spin transport as very long spin relaxation
+times and lengths can be achieved even at room temperature. However, electrical
+spin injection is challenging due to the conductivity mismatch problem. Spin
+pumping driven by ferromagnetic resonance is a neat way to circumvent this
+problem as it produces a pure spin current in the absence of a charge current.
+Here, we show spin pumping into single layer graphene in micron scale devices.
+A broadband on-chip RF current line is used to bring micron scale permalloy
+(Ni$_{80}$Fe$_{20}$) pads to ferromagnetic resonance with a magnetic field
+tunable resonance condition. At resonance, a spin current is emitted into
+graphene, which is detected by the inverse spin hall voltage in a close-by
+platinum electrode. Clear spin current signals are detected down to a power of
+a few milliwatts over a frequency range of 2 GHz to 8 GHz. This compact device
+scheme paves the way for more complex device structures and allows the
+investigation of novel materials.",1806.09356v1
+2018-09-04,Increasing the performance of the superconducting spin valve using a Heusler alloy,"We have studied superconducting properties of the spin-valve thin layer
+heterostructures CoO$_x$/F1/Cu/F2/Cu/Pb where the ferromagnetic F1 layer was
+standardly made of Permalloy whereas for the F2 layer we have taken a specially
+prepared film of the Heusler alloy Co$_2$Cr$_{1-x}$Fe$_x$Al with a small degree
+of spin polarization of the conduction band. The heterostructures demonstrate a
+significant superconducting spin-valve effect, i.e. a complete switching on and
+off of the superconducting current flowing through the system by manipulating
+the mutual orientations of the magnetization of the F1 and F2 layers. The
+magnitude of the effect is doubled in comparison with the previously studied
+analogous multilayers with the F2 layer made of the strong ferromagnet Fe.
+Theoretical analysis shows that a drastic enhancement of the switching effect
+is due to a smaller exchange field in the heterostructure coming from the
+Heusler film as compared to Fe. This enables to approach almost ideal
+theoretical magnitude of the switching in the Heusler-based multilayer with the
+F2 layer thickness of $\sim 1$\,nm.",1809.00876v1
+2018-09-17,On the speed of domain walls in thin nanotubes: the transition from the linear to the magnonic regime,"Numerical simulations of domain wall propagation in thin nanotubes when an
+external magnetic field is applied along the nanotube axis have shown an
+unexpected behavior described as a transition from a linear to a magnonic
+regime. As the applied magnetic field increases, the initial regime of linear
+growth of the speed with the field is followed by a sudden change in slope
+accompanied by the emission of spin waves. In this work an analytical formula
+for the speed of the domain wall that explains this behavior is derived by
+means of an asymptotic study of the Landau Lifshitz Gilbert equation for thin
+nanotubes. We show that the dynamics can be reduced to a one dimensional
+hyperbolic reaction diffusion equation, namely, the damped double Sine Gordon
+equation, which shows the transition to the magnonic regime as the domain wall
+speed approaches the speed of spin waves. This equation has been previously
+found to describe domain wall propagation in weak ferromagnets with the
+mobility proportional to the Dzyaloshinskii-Moriya interaction constant, for
+Permalloy nanotubes the mobility is proportional to the nanotube radius.",1809.06278v3
+2018-11-13,Enhanced domain wall velocity near a ferromagnetic instability,"Assuming a Fermi liquid behavior for $s$-conduction electrons, we rewrite the
+extended Landau-Lifshitz-Gilbert (LLG) equation renormalized by interactions
+through the Landau parameters $F^{a}_{l}$ ($l=0,1,2 \cdots$) in an explicit
+form to describe the dynamic of a domain wall (DW) due to spin transfer torque
+phenomenon. The interaction between spins of the \textit{s}-conduction
+electrons explains qualitatively the DW velocity experimental observations in
+$\mathrm{Ni_{81}}\mathrm{Fe_{19}}$ (Permalloy) recalculated by us without
+defects or impurity hypothesis. Close to Stoner ferromagnetic instability point
+where $F^{a}_{0} \approx -0.99$, the DW velocity becomes high
+($v^{*}_{DW}\approx 600$ $ms^{-1}$) and critical spin current density becomes
+reduced ($j^{*}_{c}\approx1\times10^{12}$ $Am^{-2}$) when compared to that
+calculated by nonadiabatic approach. At the critical point, the DW velocity
+diverges while critical spin current density at the same point goes to zero.
+Our theory also provides a prediction to looking for materials in which is
+possible applies a smallest critical spin current density and observes higher
+DW velocity.",1811.05380v4
+2018-11-14,Relation between spin Hall effect and anomalous Hall effect in 3$d$ ferromagnetic metals,"We study the mechanisms of the spin Hall effect (SHE) and anomalous Hall
+effect (AHE) in 3$d$ ferromagnetic metals (Fe, Co, permalloy
+(Ni$_{81}$Fe$_{19}$; Py), and Ni) by varying their resistivities and
+temperature. At low temperatures where the phonon scattering is negligible, the
+skew scattering coefficients of the SHE and AHE in Py are related to its spin
+polarization. However, this simple relation breaks down for Py at higher
+temperatures as well as for the other ferromagnetic metals at any temperature.
+We find that, in general, the relation between the SHE and AHE is more complex,
+with the temperature dependence of the SHE being much stronger than that of
+AHE.",1811.05589v2
+2019-11-03,Nanowire magnetic force sensors fabricated by focused electron beam induced deposition,"We demonstrate the use of individual magnetic nanowires (NWs), grown by
+focused electron beam induced deposition (FEBID), as scanning magnetic force
+sensors. Measurements of their mechanical susceptibility, thermal motion, and
+magnetic response show that the NWs posses high-quality flexural mechanical
+modes and a strong remanent magnetization pointing along their long axis.
+Together, these properties make the NWs excellent sensors of weak magnetic
+field patterns, as confirmed by calibration measurements on a micron-sized
+current-carrying wire and magnetic scanning probe images of a permalloy disk.
+The flexibility of FEBID in terms of the composition, geometry, and growth
+location of the resulting NWs, makes it ideal for fabricating scanning probes
+specifically designed for imaging subtle patterns of magnetization or current
+density.",1911.00912v1
+2019-11-03,Magnetic damping modulation in $IrMn_{3}/Ni_{80}Fe_{20}$ via the magnetic spin Hall effect,"Non-collinear antiferromagnets can have additional spin Hall effects due to
+the net chirality of their magnetic spin structure, which provides for more
+complex spin-transport phenomena compared to ordinary non-magnetic materials.
+Here we investigated how ferromagnetic resonance of permalloy
+($Ni_{80}Fe_{20}$) is modulated by spin Hall effects in adjacent epitaxial
+$IrMn_{3}$ films. We observe a large dc modulation of the ferromagnetic
+resonance linewidth for currents applied along the [001] $IrMn_{3}$ direction.
+This very strong angular dependence of spin-orbit torques from dc currents
+through the bilayers can be explained by the magnetic spin Hall effect where
+$IrMn_{3}$ provides novel pathways for modulating magnetization dynamics
+electrically.",1911.00943v1
+2020-01-08,Assessing different approaches to ab initio calculations of spin wave stiffness,"Ab initio calculations of the spin wave stiffness constant $D$ for elemental
+Fe and Ni performed by different groups in the past have led to values with a
+considerable spread of 50-100 %. We present results for the stiffness constant
+$D$ of Fe, Ni, and permalloy Fe$_{0.19}$Ni$_{0.81}$ obtained by three different
+approaches: (i) by finding the quadratic term coefficient of the power
+expansion of the spin wave energy dispersion, (ii) by a damped real-space
+summation of weighted exchange coupling constants, and (iii) by integrating the
+appropriate expression in reciprocal space. All approaches are implemented by
+means of the same Korringa-Kohn-Rostoker (KKR) Green function formalism. We
+demonstrate that if properly converged, all procedures yield comparable values,
+with uncertainties of 5-10 % remaining. By a careful analysis of the influence
+of various technical parameters we estimate the margin of errors for the
+stiffness constants evaluated by different approaches and suggest procedures to
+minimize the risk of getting incorrect results.",2001.02558v2
+2021-07-05,Identifying intrinsic and extrinsic mechanisms of anisotropic magnetoresistance with terahertz probes,"Identifying the intrinsic and extrinsic origins of magneto-transport in
+spin-orbit coupled systems has long been a central theme in condensed matter
+physics. However, it has been elusive owing to the lack of an appropriate
+experimental tool. In this work, using terahertz time-domain spectroscopy, we
+unambiguously disentangle the intrinsic and extrinsic contributions to the
+anisotropic magnetoresistance (AMR) of a permalloy film. We find that the
+scattering-independent intrinsic contribution to AMR is sizable and is as large
+as the scattering-dependent extrinsic contribution to AMR. Moreover, the
+portion of intrinsic contribution to total AMR increases with increasing
+temperature due to the reduction of extrinsic contribution. Further
+investigation reveals that the reduction of extrinsic contribution is caused by
+the phonon/magnon-induced negative AMR. Our result will stimulate further
+researches on other spin-orbit-interaction-induced phenomena for which
+identifying the intrinsic and extrinsic contributions is important.",2107.01770v1
+2021-07-21,Pinning and gyration dynamics of magnetic vortices revealed by correlative Lorentz and bright-field imaging,"Topological magnetic textures are of great interest in various scientific and
+technological fields. To allow for precise control of nanoscale magnetism, it
+is of great importance to understand the role of intrinsic defects in the host
+material. Here, we use conventional and time-resolved Lorentz microscopy to
+study the effect of grain size in polycrystalline permalloy films on the
+pinning and gyration orbits of vortex cores inside magnetic nanoislands. To
+assess static pinning, we use in-plane magnetic fields to shift the core across
+the island while recording its position. This enables us to produce highly
+accurate two-dimensional maps of pinning sites. Based on this technique, we can
+generate a quantitative map of the pinning potential for the core, which we
+identify as being governed by grain boundaries. Furthermore, we investigate the
+effects of pinning on the dynamic behavior of the vortex core using
+stroboscopic Lorentz microscopy, harnessing a new photoemission source that
+accelerates image acquisition by about two orders of magnitude. We find
+characteristic changes to the vortex gyration in the form of increased
+dissipation and enhanced bistability in samples with larger grains.",2107.10208v1
+2017-05-16,"Note: Derivative divide, a method for the analysis of broadband ferromagnetic resonance in the frequency domain","Broadband ferromagnetic resonance (bbFMR) spectroscopy is an established
+experimental tool to quantify magnetic properties. Due to frequency-dependent
+transmission of the microwave setup, bbFMR measurements in the frequency domain
+require a suitable background removal method. Here, we present a measurement
+and data analysis protocol that allows to perform quantitative frequency-swept
+bbFMR measurements without the need for a calibration of the microwave setup.
+The method, its limitations and advantages are described in detail. Finally the
+method is applied to evaluate FMR spectra of a permalloy thin film. The
+extracted material parameters are in very good agreement with those obtained
+using a conventional analysis in field-space.",1705.05694v2
+2018-07-09,Spin wave dynamics in artificial anti spin-ice systems: experimental and theoretical investigations,"Reversed structures of artificial spin-ice systems, where elongated holes
+with elliptical shape (antidots) are arranged into a square array with two
+orthogonal sublattices, are referred to as anti-squared spin-ice. Using
+Brillouin light scattering spectroscopy and plane wave method calculations, we
+investigate the spin wave propagation perpendicular to the applied field
+direction for two 20 nm thick Permalloy nanostructures which differ by the
+presence of single and double elliptical antidots. For the spin waves
+propagation along the principal antidot lattice axis, the spectrum consists of
+flat bands separated by several frequency gaps which are the effect of spin
+wave amplitude confinement in the regions between antidots. Contrarily, for
+propagation direction at 45 degrees with respect to the antidot symmetry axis,
+straight and narrow channels of propagation are formed, leading to broadening
+of bands and closing of the magnonics gaps. Interestingly, in this case, extra
+magnonic band gaps occur due to the additional periodicity along this
+direction. The width and the position of these gaps depend on the presence of
+single or double antidots. In this context, we discuss possibilities for the
+tuning of spin wave spectra in anti-squared spin ice structures.",1807.03016v1
+2018-07-27,Optimization of Multi-Frequency Magnonic Waveguides with Enhanced Group Velocities by Exchange Coupled Ferrimagnet/Ferromagnet Bilayers,"We report broadband spectroscopy and numerical analysis by which we explore
+propagating spin waves in a magnetic bilayer consisting of a 23 nm thick
+permalloy film deposited on 130 nm thick $Y_{3}Fe_{5}O_{12}$. In the bilayer,
+we observe a characteristic mode that exhibits a considerably larger group
+velocity at small in-plane magnetic field than both the magnetostatic and
+perpendicular standing spin waves. Using the finite element method, we confirm
+the observations by simulating the mode profiles and dispersion relations. They
+illustrate the hybridization of spin wave modes due to exchange coupling at the
+interface. The high-speed propagating mode found in the bilayer can be utilized
+to configure multi-frequency spin wave channels enhancing the performance of
+spin wave based logic devices.",1807.10508v2
+2018-10-05,Remagnetization in the array of ferromagnetic nanowires with periodic and quasiperiodic order,"We investigate experimentally and theoretically the magnetization reversal
+process in one-dimensional magnonic structures composed of permalloy nanowires
+of the two different widths and finite length arranged in a periodic and
+quasiperiodic order. The main features of the hysteresis loop are determined by
+different shape anisotropies of the component elements and the dipolar
+interactions between them. We showed, that the dipolar interactions between
+nanowires forming a ribbon can be controlled by change a distance between the
+neighboring ribbons. The quasiperiodic order can influence the hysteresis loop
+by introduction additional tiny switching steps when the dipolar interactions
+are sufficiently strong.",1810.02796v1
+2018-10-09,Non-uniform spin wave softening in 2D magnonic crystals as a tool for opening omnidirectional magnonic band gaps,"By means of the plane wave method we study spin wave dynamics in
+two-dimensional bi-component magnonic crystals based on a squeezed hexagonal
+lattice and consist of a permalloy thin film with cobalt inclusions. We explore
+the dependence of a spin wave frequency on the external magnetic field,
+especially in weak fields where the mode softening takes place. For considered
+structures, the mode softening proves to be highly non-uniform on both the mode
+number and the wave vector. We found this effect to be responsible for the
+omnidirectional band gap opening. Moreover, we show that the enhancement of the
+demagnetizing field caused by the squeezing of the structure is of crucial
+importance for the non-uniform mode softening. This allows us to employ this
+mechanism to design magnonic gaps with different sensitivity for the tiny
+change of the external field. The effects we have found should be useful in
+designing and optimization of spin wave filters highly tunable by a small
+external magnetic field.",1810.04005v3
+2018-10-19,Magnon properties of random alloys,"We study magnon properties in terms of spin stiffness, Curie temperatures and
+magnon spectrum of Fe-Ni, Co-Ni and Fe-Co random alloys using a combination of
+electronic structure calculations and atomistic spin dynamics simulations.
+Influence of the disorder are studied in detail by use of large supercells with
+random atomic arrangement. It is found that disorder affects the magnon
+spectrum in vastly different ways depending on the system. Specifically, it is
+more pronounced in Fe-Ni alloys compared to Fe-Co alloys. In particular, the
+magnon spectrum at room temperature in Permalloy (Fe$_{20}$Ni$_{80}$) is found
+to be rather diffuse in a large energy interval while in Fe$_{75}$Co$_{25}$ it
+forms sharp branches. Fe-Co alloys are very interesting from a technological
+point of view due to the combination of large Curie temperatures and very low
+calculated Gilbert damping of $\sim$0.0007 at room temperature for Co
+concentrations around 20--30\%.",1810.08487v1
+2018-10-31,"Comment on ""Optical detection of transverse spin-Seebeck effect in permalloy film using Sagnac interferometer microscopy""","Measuring spin currents and spin accumulations is challenging. This is mainly
+because of their small size and the lack of a standard spin detector comparable
+to conventional ampere meters or voltage detectors. It is all the more pleasing
+to hear about new methods for detecting spin currents and spin accumulations. A
+recent example is the paper of McLaughlin et al. [Phys. Rev. B 95, 180401
+(2017)], who report novel measurements of the transverse spin-Seebeck effect
+(TSSE) in metals by optical means using a Sagnac interferometer microscope.
+However, because no standard procedures or reference measurements are available
+for verification, critical discussions are crucial for evaluation of such novel
+experimental approaches. In our comment, we estimate the size of the effect
+observed by McLaughlin et al. To illustrate that the estimated size is
+exceptionally large, we use a comparison with another spin-caloritronic effect:
+the spin-dependent Seebeck effect. Such a large TSSE is in contradiction with
+previous experiments that could not resolve a TSSE signal. Therefore, we
+suggest that signal measured by McLaughlin et al. is not or not only caused by
+the TSSE.",1810.13220v1
+2019-01-07,Simultaneous Optical and Electrical Spin-Torque Magnetometry with Stroboscopic Detection of Spin-Precession Phase,"Spin-based coherent information processing and encoding utilize the
+precession phase of spins in magnetic materials. However, the detection and
+manipulation of spin precession phases remain a major challenge for advanced
+spintronic functionalities. By using simultaneous electrical and optical
+detection, we demonstrate the direct measurement of the precession phase of
+Permalloy ferromagnetic resonance driven by the spin-orbit torques from
+adjacent heavy metals. The spin Hall angle of the heavy metals can be
+independently determined from concurrent electrical and optical signals. The
+stroboscopic optical detection also allows spatially measuring local
+spin-torque parameters and the induced ferromagnetic resonance with
+comprehensive amplitude and phase information. Our study offers a route towards
+future advanced characterizations of spin-torque oscillators, magnonic
+circuits, and tunnelling junctions, where measuring the current-induced spin
+dynamics of individual nanomagnets are required.",1901.01923v1
+2019-01-25,Current-Induced Torques with Dresselhaus Symmetry Due to Resistance Anisotropy in 2D Materials,"We report measurements of current-induced torques in heterostructures of
+Permalloy (Py) with TaTe$_2$, a transition-metal dichalcogenide (TMD) material
+possessing low crystal symmetry, and observe a torque component with
+Dresselhaus symmetry. We suggest that the dominant mechanism for this
+Dresselhaus component is not a spin-orbit torque, but rather the Oersted field
+arising from a component of current that flows perpendicular to the applied
+voltage due to resistance anisotropy within the TaTe$_2$. This type of
+transverse current is not present in wires made from a single uniform layer of
+a material with resistance anisotropy, but will result whenever a material with
+resistance anisotropy is integrated into a heterostructure with materials
+having different resistivities, thereby producing a spatially non-uniform
+pattern of current flow. This effect will therefore influence measurements in a
+wide variety of heterostructures incorporating 2D TMD materials and other
+materials with low crystal symmetries.",1901.08908v1
+2019-07-15,Tuning edge localized spin waves in magnetic microstripes by proximate magnetic structures,"The propagation of edge localized spin waves (E-SWs) in yttrium iron garnet
+(YIG) microstripes with/without the proximate magnetic microstructures is
+investigated by micromagnetic simulations. A splitting of the dispersion curve
+with the presence of permalloy (Py) stripe is also observed. The E-SWs on the
+two edges of YIG stripe have different wavelengths, group velocities, and decay
+lengths at the same frequencies. The role of the Py stripe was found to be the
+source of the inhomogeneous static dipolar field without dynamic coupling with
+YIG. This work opens new perspectives for the design of innovative SW
+interference-based logic devices.",1907.06718v1
+2019-10-11,Investigation of spin orbit torque driven dynamics in ferromagnetic heterostructures,"We use time-resolved (TR) measurements based on the polar magneto-optical
+Kerr effect (MOKE) to study the magnetization dynamics excited by spin orbit
+torques in Py (Permalloy)/Pt and Ta/CoFeB bilayers. The analysis reveals that
+the field-like (FL) spin orbit torque (SOT) dominates the amplitude of the
+first oscillation cycle of the magnetization precession and the damping-like
+(DL) torque determines the final steady-state magnetization. In our bilayer
+samples, we have extracted the effective fields, hFL and hDL, of the two SOTs
+from the time-resolved magnetization oscillation spectrum. The extracted values
+are in good agreement with those extracted from time-integrated DCMOKE
+measurements, suggesting that the SOTs do not change at high frequencies. We
+also find that the amplitude ratio of the first oscillation to steady state is
+linearly proportional to the ratio hFL/hDL. The first oscillation amplitude is
+inversely proportional to, whereas the steady state value is independent of,
+the applied external field along the current direction.",1910.04945v1
+2019-10-16,Spin-Wave frequency division multiplexing in an yttrium iron garnet microstripe magnetized by inhomogeneous field,"Spin waves are promising candidates for information processing and
+transmission in a broad frequency range. In the realization of magnonic
+devices, the frequency depended division of the spin wave frequencies is a
+critical function for parallel information processing. In this work, we
+demonstrate a proof-of-concept spin-wave frequency division multiplexing method
+by magnetizing a homogenous magnetic microstripe with an inhomogeneous field.
+The symmetry breaking additional field is introduced by a permalloy stripe
+simply placed in lateral proximity to the waveguide. Spin waves with different
+frequencies can propagate independently, simultaneously and separately in space
+along the shared waveguide. This work brings new potentials for parallel
+information transmission and processing in magnonics.",1910.07136v1
+2019-10-30,Understanding Thermal Annealing of Artificial Spin Ice,"We have performed a detailed study of thermal annealing of the moment
+configuration in artificial spin ice. Permalloy (Ni$_{80}$Fe$_{20}$) artificial
+spin ice samples were examined in the prototypical square ice geometry,
+studying annealing as a function of island thickness, island shape, and
+annealing temperature and duration. We also measured the Curie temperature as a
+function of film thickness, finding that thickness has a strong effect on the
+Curie temperature in regimes of relevance to many studies of the dynamics of
+artificial spin ice systems. Increasing the interaction energy between island
+moments and reducing the energy barrier to flipping the island moments allows
+the system to more closely approach the collective low energy state of the
+moments upon annealing, suggesting new channels for understanding the
+thermalization processes in these important model systems.",1910.14158v1
+2019-10-31,Coherent spin pumping in a strongly coupled magnon-magnon hybrid system,"We experimentally identify coherent spin pumping in the magnon-magnon hybrid
+modes of permalloy/yttrium iron garnet (Py/YIG) bilayers. Using broadband
+ferromagnetic resonance, an ""avoided crossing"" is observed between the uniform
+mode of Py and the spin wave mode of YIG due to the fieldlike interfacial
+exchange coupling. We also identify additional linewidth suppression and
+enhancement for the in-phase and out-of-phase hybrid modes, respectively,
+\textcolor{black}{which can be interpreted as concerted dampinglike torque from
+spin pumping}. Our analysis predicts inverse proportionality of both fieldlike
+and dampinglike torques to the square root of the Py thickness, which
+quantitatively agrees with experiments.",1910.14470v2
+2012-09-04,Microscopic Theory of Magnon-Drag Thermoelectric Transport in Ferromagnetic Metals,"A theoretical study of the magnon-drag Peltier and Seebeck effects in
+ferromagnetic metals is presented. A magnon heat current is described
+perturbatively from the microscopic viewpoint with respect to electron--magnon
+interactions and the electric field. Then, the magnon-drag Peltier coefficient
+$\Pi_\MAG$ is obtained as the ratio between the magnon heat current and the
+electric charge current. We show that $\Pi_\MAG=C_\MAG T^{5/2}$ at a low
+temperature $T$; that the coefficient $C_\MAG$ is proportional to the spin
+polarization $P$ of the electric conductivity; and that $P>0$ for $C_\MAG<0$,
+but $P<0$ for $C_\MAG>0$. From experimental results for magnon-drag Peltier
+effects, we estimate that the strength of the electron--magnon interaction is
+about 0.3 eV$\cdot\AA^{3/2}$ for permalloy.",1209.0685v2
+2012-09-21,Broadband probing magnetization dynamics of the coupled vortex state permalloy layers in nanopillars,"Broadband magnetization response of coupled vortex state magnetic dots in
+layered nanopillars was explored as a function of in-plane magnetic field and
+interlayer separation. For dipolarly coupled circular Py(25 nm)/Cu(20 nm)/Py(25
+nm) nanopillars of 600 nm diameter, a small in-plane field splits the
+eigenfrequencies of azimuthal spin wave modes inducing an abrupt transition
+between in-phase and out-of-phase kinds of the low-lying coupled spin wave
+modes. The critical field for this splitting is determined by antiparallel
+chiralities of the vortices in the layers. Qualitatively similar (although more
+gradual) changes occur also in the exchange coupled Py(25 nm)/Cu(1 nm)/Py(25
+nm) tri-layer nanopillars. These findings are in qualitative agreement with
+micromagnetic dynamic simulations.",1209.4822v1
+2014-06-27,Observation of propagating edge spin waves modes,"Broadband magnetization response of equilateral triangular 1000 nm Permalloy
+dots has been studied under an in-plane magnetic field, applied parallel
+(buckle state) and perpendicular (Y state) to the triangles base. Micromagnetic
+simulations identify edge spin waves (E-SWs) in the buckle state as SWs
+propagating along the two adjacent edges. These quasi one-dimensional spin
+waves emitted by the vertex magnetic charges gradually transform from
+propagating to standing due to interference and are weakly affected by dipolar
+interdot interaction and variation of the aspect ratio. Spin waves in the Y
+state have a two dimensional character. These findings open perspectives for
+implementation of the E-SWs in magnonic crystals and thin films.",1406.7186v1
+2014-06-27,Spin waves along the edge states,"Spin waves have been studied experimentally and by simulations in 1000 nm
+side equilateral triangular Permalloy dots in the Buckle state (B, with
+in-plane field along the triangle base) and the Y state (Y, with in-plane field
+perpendicular to the base). The excess of exchange energy at the triangles
+edges creates channels that allow effective spin wave propagation along the
+edges inthe B state. These quasi one-dimensional spin waves emitted by the
+vertex magnetic charges gradually transform from propagating to standing due to
+interference and(as pointed out by simulations) areweakly affected by
+smallvariations of the aspect ratio(from equilateral to isosceles dots) or by
+interdot dipolar interaction present in our dot arrays. Spin waves excited in
+the Y state have mainly a two-dimensional character.Propagation of the spin
+waves along the edge states in triangular dots opens possibilities for creation
+of new and versatile spintronic devices.",1406.7200v1
+2018-02-12,Spin-orbit torque and spin pumping in YIG/Pt with interfacial insertion layers,"We experimentally investigate spin-orbit torque and spin pumping in
+Y$_3$Fe$_5$O$_{12}$(YIG)/Pt bilayers with ultrathin insertion layers at the
+interface. An insertion layer of Cu suppresses both spin-orbit torque and spin
+pumping, whereas an insertion layer of Ni$_{80}$Fe$_{20}$ (permalloy, Py)
+enhances them, in a quantitatively consistent manner with the reciprocity of
+the two spin transmission processes. However, we observe a large enhancement of
+Gilbert damping with the insertion of Py that cannot be accounted for solely by
+spin pumping, suggesting significant spin-memory loss due to the interfacial
+magnetic layer. Our findings indicate that the magnetization at the YIG-metal
+interface strongly influences the transmission and depolarization of pure spin
+current.",1802.03865v3
+2018-02-18,New Description of Evolution of Magnetic Phases in Artificial Honeycomb Lattice,"Artificial magnetic honeycomb lattice provides a two-dimensional archetypal
+system to explore novel phenomena of geometrically frustrated magnets.
+According to theoretical reports, an artificial magnetic honeycomb lattice is
+expected to exhibit several phase transitions to unique magnetic states as a
+function of reducing temperature. Experimental investigations of permalloy
+artificial honeycomb lattice of connected ultra- small elements, ~ 12 nm,
+reveal a more complicated behavior. First, upon cooling the sample to
+intermediate temperature, T ~ 175 K, the system manifests a non-unique state
+where the long range order co-exists with short-range magnetic charge order and
+weak spin ice state. Second, at much lower temperature, T ~ 6 K, the long-range
+spin solid state exhibits a re-entrant behavior. Both observations are in
+direct contrast to the present understanding of this system. New theoretical
+approaches are needed to develop a comprehensive formulation of this two
+dimensional magnet.",1802.06323v1
+2018-02-19,Temperature Dependent Magnetism in Artificial Honeycomb Lattice of Connected Elements,"Artificial magnetic honeycomb lattices are expected to exhibit a broad and
+tunable range of novel magnetic phenomena that would be difficult to achieve in
+natural materials, such as long-range spin ice, entropy-driven magnetic
+charge-ordered state and spin-order due to the spin chirality. Eventually, the
+spin correlation is expected to develop into a unique spin solid state density
+ground state, manifested by the distribution of the pairs of vortex states of
+opposite chirality. Here we report the creation of a new artificial permalloy
+honeycomb lattice of ultra-small connecting bonds, with a typical size of
+$\simeq$ 12 nm. Detail magnetic and neutron scattering measurements on the
+newly fabricated honeycomb lattice demonstrate the evolution of magnetic
+correlation as a function of temperature. At low enough temperature, neutron
+scattering measurements and micromagnetic simulation suggest the development of
+loop state of vortex configuration in this system.",1802.06631v1
+2018-08-06,Spin wave dispersion and intensity correlation in width-modulated nanowire arrays: A Brillouin light scattering study,"Using Brillouin light scattering spectroscopy and dynamical matrix method
+calculations, we study collective spin waves in dense arrays of periodically
+double-side width-modulated Permalloy nanowires. Width modulation is achieved
+by creating a sequence of triangular notches on the two parallel nanowire
+sides, with a periodicity of p=1000 nm, and tunable relative displacement (D)
+of the notches sequence on the two lateral sides. Both symmetric (D=0) and
+asymmetric (D= 250 and 500 nm) width-modulated nanowires were investigated. We
+have found that the detected modes have Bloch-type character and belong to a
+doublet deriving from the splitting of the modes characteristics of the
+nanowire with homogeneous width. Interestingly, the amplitude of the magnonic
+band, the frequency difference of the doublet, as well as their relative
+scattering intensity, can be efficiently controlled by increasing D rather than
+having single- or symmetric (D=0) double-side width-modulation.",1808.01732v1
+2018-08-10,Ferromagnetic Josephson junctions for cryogenic memory,"Josephson junctions containing ferromagnetic materials have attracted intense
+interest both because of their unusual physical properties and because they
+have potential application for cryogenic memory. There are two ways to store
+information in such a junction: either in the amplitude of the critical current
+or in the ground-state phase difference across the junction; the latter is the
+topic of this paper. We have recently demonstrated two different ways to
+achieve phase control in such junctions: the first uses junctions containing
+two magnetic layers in a ""pseudo spin valve"" configuration, while the second
+uses junctions containing three magnetic layers with non-collinear
+magnetizations. The demonstration devices, however, have not yet been optimized
+for use in a large-scale cryogenic memory array. In this paper we outline some
+of the issues that must be considered to perform such an optimization, and we
+provide a speculative ""phase-diagram"" for the nickel-permalloy spin-valve
+system showing which combinations of ferromagnetic layer thicknesses should
+produce useful devices.",1808.03639v1
+2018-08-28,An Intrinsic Spin Orbit Torque Nano-Oscillator,"Spin torque and spin Hall effect nanooscillators generate high intensity spin
+wave auto oscillations on the nanoscale enabling novel microwave applications
+in spintronics, magnonics, and neuromorphic computing. For their operation,
+these devices require externally generated spin currents either from an
+additional ferromagnetic layer or a material with a high spin Hall angle. Here
+we demonstrate highly coherent field and current tunable microwave signals from
+nanoconstrictions in single 15 and 20 nm thick permalloy layers. Using a
+combination of spin torque ferromagnetic resonance measurements, scanning
+microBrillouin light scattering microscopy, and micromagnetic simulations, we
+identify the autooscillations as emanating from a localized edge mode of the
+nanoconstriction driven by spin orbit torques. Our results pave the way for
+greatly simplified designs of auto oscillating nanomagnetic systems only
+requiring a single ferromagnetic layer.",1808.09330v1
+2019-06-01,Coherent ac spin current transmission across an antiferromagnetic CoO insulator,"The recent discovery of spin-current transmission through antiferromagnetic
+(AFM) insulating materials opens up unprecedented opportunities for fundamental
+physics and spintronics applications. The great mystery currently surrounding
+this topic is: how could THz AFM magnons mediate a GHz spin current? This
+mis-match of frequencies becomes particularly critical for the case of coherent
+ac spin-current, raising the fundamental question of whether a GHz ac
+spin-current can ever keep its coherence inside an AFM insulator and so drive
+the spin precession of another FM layer coherently? Utilizing element- and
+time-resolved x-ray pump-probe measurements on Py/Ag/CoO/Ag/Fe75Co25/MgO(001)
+heterostructures, we demonstrate that a coherent GHz ac spin current pumped by
+the permalloy (Py) ferromagnetic resonance (FMR) can transmit coherently across
+an antiferromagnetic CoO insulating layer to drive a coherent spin precession
+of the FM Fe75Co25 layer. Further measurement results favor thermal magnons
+rather than evanescent spin waves as the mediator of the coherent ac spin
+current in CoO.",1906.00155v1
+2019-06-16,Tunable Magnetic Domain Walls for Therapeutic Neuromodulation at Cellular Level: Stimulating Neurons Through Magnetic Nanowires,"Cellular-level neuron stimulation has attracted much attention in the areas
+of prevention, diagnosis and treatment of neurological disorders. Herein, we
+propose a spintronic neurostimulator based on the domain wall movement inside
+stationary magnetic nanowires driven by the spin transfer torque. The
+electromotive forces generated by the domain wall motion can serve as highly
+localized stimulation signals for neuron cells. Our simulation results show
+that the induced electric field from the domain wall motion in permalloy
+nanowires can reach up to 14 V/m, which is well above the reported threshold
+stimulation signal for clinical applications. The proposed device operates on a
+current range of several uA which is 10^3 times lower compared to magnetic
+stimulation by microcoils. The duration and amplitude of the stimulating signal
+can be controlled by adjusting the applied current density, the geometry of the
+nanowire, and the magnetic properties of the nanowire material.",1906.08701v1
+2020-04-08,Charge-to-spin conversion efficiency in ferromagnetic nanowires by spin torque ferromagnetic resonance: Reconciling lineshape and linewidth analysis methods,"Spin orbit torques are of great interest for switching the magnetization
+direction in nanostructures, moving skyrmions and exciting spin waves. The
+standard method of determining their efficiency is by spin torque ferromagnetic
+resonance (ST-FMR), a technique that involves analyzing the resonance linewidth
+or lineshape. On microstuctures these two analysis methods are quite
+consistent. Here we present ST-FMR results on permalloy (Ni$_{80}$Fe$_{20}$)
+nanowires -- with widths varying from $150$ to 800 nm -- that show that the
+standard model used to analyze the resonance linewidth and lineshape give
+different results; the efficiency appears greatly enhanced in nanowires when
+the lineshape method is used. A ST-FMR model that properly accounts for the
+sample shape is presented and shows much better consistency between the two
+methods. Micromagnetic simulations are used to verify the model. These results
+and the more accurate nanowire model presented are of importance for
+characterizing and optimizing charge-to-spin conversion efficiencies in
+nanostructures.",2004.03784v1
+2020-05-03,Unconventional spin-orbit torque in transition metal dichalcogenide/ferromagnet bilayers from first-principles calculations,"Motivated by recent observations of unconventional out-of-plane dampinglike
+torque in \ch{WTe2}/Permalloy bilayer systems, we calculate the spin-orbit
+torque generated in two-dimensional transition metal dichalcogenide
+(TMD)-ferromagnet heterostructures using first-principles methods and linear
+response theory. Our numerical calculation of spin-orbit torques in
+\ch{WTe2}/Co and \ch{MoTe2}/Co heterostructures shows both conventional and
+novel dampinglike torkances (torque per electric field) with comparable
+magnitude, around $100~\hbar/2e~(\rm \Omega\cdot cm)^{-1}$, for an electric
+field applied perpendicular to the mirror plane of the TMD layer. To gain
+further insight into the source of dampinglike torque, we compute the spin
+current flux between the TMD and Co layers and find good agreement between the
+two quantities. This indicates that the conventional picture of dampinglike
+spin-orbit torque, whereby the torque results from the spin Hall effect plus
+spin transfer torque, largely applies to TMD/Co bilayer systems.",2005.01109v2
+2022-03-30,Hybrid magnonics for short-wavelength spin waves facilitated by a magnetic heterostructure,"Recent research on hybrid magnonics has been restricted by the long magnon
+wavelengths of the ferromagnetic resonance modes. We present an experiment on
+the hybridization of 250-nm wavelength magnons with microwave photons in a
+multimode magnonic system consists of a planar cavity and a magnetic bilayer.
+The coupling between magnon modes in the two magnetic layers, i.e., the uniform
+mode in Permalloy (Py) and the perpendicular standing spin waves (PSSWs) in
+YIG, serves as an effective means for exciting short-wavelength PSSWs, which is
+further hybridized with the photon mode of the microwave resonator. The
+demonstrated magnon-photon coupling approaches the superstrong coupling regime,
+and can even be achieved near zero bias field.",2203.16310v1
+2016-03-15,Ordering in rolled-up single-walled ferromagnetic nanomembranes,"Magnetization of soft-ferromagnetic nano- and microtubes of nanometer-thin
+walls (a single-widening rolled-up nanomembranes) is theoretically studied
+using analytical and numerical approaches including different stress-induced
+anisotropies. Within the analytical study, we consider magnetostatic effects
+qualitatively, with an effective anisotropy, while they are fully treated in
+the micromagnetic simulations (limited to the tubes of submicrometer diameters
+however). Basic types of the periodic ordering have been established and their
+presence in nanotubes of polycrystalline Permalloy and cobalt has been verified
+within the simulations. The domain structure is basically determined by a
+material-deposition-induced helical stress or a cooling-induced axial stress
+via the volume magnetostriction while it is influenced by the distribution of
+magnetic charges as well. Also, it is dependent on the initial state of the
+magnetization process.",1603.04883v2
+2016-11-20,Selective sensitivity in Kerr microscopy,"A new technique for contrast separation in wide-field magneto-optical Kerr
+microscopy is introduced. Utilizing the light from eight light emitting diodes,
+guided to the microscope by glass fibers and being switched synchronously with
+the camera exposure, domain images with orthogonal in-plane sensitivity can be
+displayed simultaneously at real-time and images with pure in-plane or polar
+contrast can be obtained. The benefit of this new method of contrast separation
+is demonstrated for permalloy films, a NdFeB sinter magnet, and a cobalt
+crystal. Moreover, the new technique is shown to strongly enhance the
+sensitivity of Kerr microscopy by eliminating parasitic contrast contributions
+occurring in conventional setups. A doubling of the in-plane domain contrast
+and a sensitivity to Kerr rotations as low as 0.6~mdeg is demonstrated",1612.02027v1
+2017-02-16,Extended spin model in atomistic simulations of alloys,"An extended atomistic spin model allowing for studies of the finite
+temperature magnetic properties of alloys is proposed. The model is obtained by
+extending the Heisenberg Hamiltonian via a parameterization from a first
+principles basis, interpolating from both the low temperature ferromagnetic and
+the high temperature paramagnetic reference states. This allows us to treat
+magnetic systems with varying degree of itinerant character within the model.
+Satisfactory agreement with both previous theoretical studies and experiments
+are obtained in terms of Curie temperatures and paramagnetic properties. The
+proposed model is not restricted to elements but is also applied to binary
+alloys, such as the technologically important material Permalloy, where
+significant differences in the finite magnetic properties of Fe and Ni magnetic
+moments are found. The proposed model strives to find the right compromise
+between accuracy and computational feasibility for accurate modeling, even for
+complex magnetic alloys and compounds.",1702.05011v1
+2017-02-22,Domain wall motion by localized temperature gradients,"Magnetic domain wall (DW) motion induced by a localized Gaussian temperature
+profile is studied in a Permalloy nanostrip within the framework of the
+stochastic Landau-Lifshitz-Bloch equation. The different contributions to
+thermally induced DW motion, entropic torque and magnonic spin transfer torque,
+are isolated and compared. The analysis of magnonic spin transfer torque
+includes a description of thermally excited magnons in the sample. A third
+driving force due to a thermally induced dipolar field is found and described.
+Finally, thermally induced DW motion is studied under realistic conditions by
+taking into account the edge roughness. The results give quantitative insights
+into the different mechanisms responsible for domain wall motion in temperature
+gradients and allow for comparison with experimental results.",1702.06725v1
+2017-06-11,Absorbing boundary layers for spin wave micromagnetics,"Micromagnetic simulations are used to investigate the effects of different
+absorbing boundary layers (ABLs) on spin waves (SWs) reflected from the edges
+of a magnetic nano-structure. We define the conditions that a suitable ABL must
+fulfill and compare the performance of abrupt, linear, polynomial and tan
+hyperbolic damping profiles in the ABL. We first consider normal incidence in a
+permalloy stripe and propose a transmission line model to quantify reflections
+and calculate the loss introduced into the stripe due to the ABL. We find that
+a parabolic damping profile absorbs the SW energy efficiently and has a low
+reflection coefficient, thus performing much better than the commonly used
+abrupt damping profile. We then investigated SWs that are obliquely incident at
+26.6, 45 and 63.4 degrees on the edge of a yttrium-iron-garnet film. The
+parabolic damping profile again performs efficiently by showing a high SW
+energy transfer to the ABL and a low reflected SW amplitude.",1706.03325v1
+2017-10-02,Quantum point contact: a case of spin-resolved electron transport,"The work presents the extended theoretical model of the electrical
+conductance in non-magnetic and magnetic nano-size point contacts. The
+developed approach describes diffusive, quasi-ballistic, ballistic and quantum
+regimes of the spin-resolved conductance. It is based on the electron transport
+through metallic junction within approach of the circular constriction. The
+model provides unified description of the contact resistance from Maxwell
+diffusive through the ballistic to purely quantum transport regimes without any
+residual terms depending from the scale. An application are given for
+experimental treatment of the golden nanocontacts as a non-magnetic case and
+Permalloy nanowire with/without domain wall as example for the magnetic system.
+The model of quantum point contact assumes that contact area can be replaced by
+the quantum object (i.e. magnetic tunnel junction, narrow domain wall, etc.),
+where potential energy profile determine its electrical properties.",1710.00496v1
+2017-10-03,Nonlocal electrical detection of spin accumulation generated by Anomalous Hall effects in mesoscopic Ni_81Fe_19 films,"Spin accumulation generated by the anomalous Hall effects (AHE) in mesoscopic
+ferromagnetic Ni81Fe19 (permalloy or Py) films is detected electrically by a
+nonlocal method. The reciprocal phenomenon, inverse spin Hall effects (ISHE),
+can also be generated and detected all-electrically in the same structure. For
+accurate quantitative analysis, a series of nonlocal AHE/ISHE structures and
+supplementary structures are fabricated on each sample substrate to account for
+statistical variations and to accurately determine all essential physical
+parameters in-situ. By exploring Py thicknesses of 4 nm, 8 nm, and 12 nm, the
+Py spin diffusion length {\lambda}_Py is found to be much shorter than the film
+thicknesses. The product of {\lambda}_Py and the Py spin Hall angle {\alpha}_SH
+is determined to be independent of thickness and resistivity:
+{\alpha}_SH*{\lambda}_Py= (0.066 +/- 0.009) nm at 5 K and (0.041 +/- 0.010) nm
+at 295 K. These values are comparable to those obtained from mesoscopic Pt
+films.",1710.01186v1
+2017-10-25,Collective spin waves in arrays of Permalloy nanowires with single-side periodically modulated width,"We have experimentally and numerically investigated the dispersion of
+collective spin waves prop-agating through arrays of longitudinally magnetized
+nanowires with periodically modulated width. Two nanowire arrays with
+single-side modulation and different periodicity of modulation were studied and
+compared to the nanowires with homogeneous width. The spin-wave dispersion,
+meas-ured up to the third Brillouin zone of the reciprocal space, revealed the
+presence of two dispersive modes for the width-modulated NWs, whose amplitude
+of magnonic band depends on the modula-tion periodicity, and a set of
+nondispersive modes at higher frequency. These findings are different from
+those observed in homogeneous width NWs where only the lowest mode exhibits
+sizeable dis-persion. The measured spin-wave dispersion has been satisfactorily
+reproduced by means of dynam-ical matrix method. Results presented in this work
+are important in view of the possible realization of frequency tunable magnonic
+device.",1710.09163v1
+2019-03-03,Near-Unity Spin Hall Ratio in Ni$_x$Cu$_{1-x}$ Alloys,"We report a large spin Hall effect in the 3$d$ transition metal alloy
+Ni$_x$Cu$_{1-x}$ for $x\in\left\{ 0.3,0.75\right\} $, detected via the
+ferromagnetic resonance of a Permalloy (Py = Ni$_{80}$Fe$_{20}$) film deposited
+in a bilayer with the alloy. A thickness series at $x$ = 0.6, for which the
+alloy is paramagnetic at room temperature, allows us to determine the spin Hall
+ratio $\theta_{\rm{SH}}\approx1$, spin diffusion length $\lambda_{\rm{s}}$,
+spin mixing conductance $G_{\uparrow\downarrow}$, and damping
+$\alpha_{\rm{SML}}$ due to spin memory loss . We compare our results with
+similar experiments on Py/Pt bilayers measured using the same method. Ab initio
+band structure calculations with disorder and spin-orbit coupling suggest an
+intrinsic spin Hall effect in Ni$_x$Cu$_{1-x}$ alloys, although the experiments
+here cannot distinguish between extrinsic and intrinsic mechanisms.",1903.00910v2
+2019-03-05,Strong Coupling between Microwave Photons and Nanomagnet Magnons,"Coupled microwave photon-magnon hybrid systems offer promising applications
+by harnessing various magnon physics. At present, in order to realize high
+coupling strength between the two subsystems, bulky ferromagnets with large
+spin numbers are utilized, which limits their potential applications for
+scalable quantum information processing. In this paper, by enhancing single
+spin coupling strength using lithographically defined superconducting
+resonators, we report high cooperativities between a resonator mode and a
+Kittel mode in nanometer thick Permalloy wires. The on-chip, lithographically
+scalable, and superconducting quantum circuit compatible design provides a
+direct route towards realizing hybrid quantum systems with nanomagnets, whose
+coupling strength can be precisely engineered and dynamic properties can be
+controlled by various mechanisms derived from spintronic studies.",1903.01887v3
+2019-03-19,Broadband magnetoelastic coupling in magphonic crystals for high-frequency nanoscale spin wave generation,"Spin waves are promising candidates for information carriers in advanced
+technology. The interactions between spin waves and acoustic waves in magnetic
+nanostructures are of much interest because of their potential application for
+spin wave generation, amplification and transduction. We investigate
+numerically the dynamics of magnetoelastic excitations in a one-dimensional
+magphonic crystal consisting of alternating layers of permalloy and cobalt. We
+use the plane wave method and the finite element method for frequency- and
+time-domain simulations, respectively. The studied structure is optimized for
+hybridization of specific spin-wave and acoustic dispersion branches in the
+entire Brillouin zone in a broad frequency range. We show that this type of
+periodic structure can be used for efficient generation of high-frequency spin
+waves.",1903.08024v1
+2019-05-02,Anomalous spin Hall angle of a metallic ferromagnet determined by a multiterminal spin injection/detection device,"We report on the determination of the anomalous spin Hall angle in the
+ferromagnetic metal alloy cobalt-iron (Co$_{25}$Fe$_{75}$, CoFe). This is
+accomplished by measuring the spin injection/detection efficiency in a
+multiterminal device with nanowires of platinum (Pt) and CoFe deposited onto
+the magnetic insulator yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$, YIG). Applying
+a spin-resistor model to our multiterminal spin transport data, we determine
+the magnon conductivity in YIG, the spin conductance at the YIG/CoFe interface
+and finally the anomalous spin Hall angle of CoFe as a function of its spin
+diffusion length in a single device. Our experiments clearly reveal a negative
+anomalous spin Hall angle of the ferromagnetic metal CoFe, but a vanishing
+ordinary spin Hall angle. This is in contrast to the results reported for the
+ferromagnetic metals Co and permalloy.",1905.00663v1
+2019-05-02,Negligible thermal contributions to the spin pumping signal in ferromagnetic metal-Platinum bilayers,"Spin pumping by ferromagnetic resonance is one of the most common technique
+to determine spin hall angles, Edelstein lengths or spin diffusion lengths of a
+large variety of materials. In recent years, rising concerns have appeared
+regarding the interpretation of these experiments, underlining that the signal
+could arise purely from thermoelectric effects, rather than from coherent spin
+pumping. Here, we propose a method to evaluate the presence or absence of
+thermal effects in spin pumping signals, by combining bolometry and spin
+pumping by ferromagnetic resonance measurements, and comparing their timescale.
+Using a cavity to perform the experiments on Pt\Permalloy and La0.7Sr0.3MnO3\Pt
+samples, we conclude on the absence of any measurable thermoelectric
+contribution such as the spin Seebeck and anomalous Nernst effects at resonance",1905.00771v2
+2019-09-04,Two-axis cavity optomechanical torque characterization of magnetic microstructures,"Significant new functionality is reported for torsion mechanical tools aimed
+at full magnetic characterizations of both spin statics and dynamics in micro-
+and nanostructures. Specifically, two orthogonal torque directions are
+monitored and the results co-analyzed to separate magnetic moment and magnetic
+susceptibility contributions to torque, as is desired for characterization of
+anisotropic three-dimensional structures. The approach is demonstrated through
+application to shape and microstructural disorder-induced magnetic anisotropies
+in lithographically patterned permalloy, and will have utility for the
+determination of important magnetic thin-film and multilayer properties
+including interface anisotropy and exchange bias. The results reflect
+remarkable sensitivity of the out-of-plane magnetic torque to the nature of
+small edge domains perpendicular to the applied field direction, and also
+contain tantalizing indications of direct coupling to spin dynamics at the
+frequency of the mechanics.",1909.01949v1
+2019-09-09,Modulation of magnon spin transport in a magnetic gate transistor,"We demonstrate a modulation of up to 18% in the magnon spin transport in a
+magnetic insulator (Y$_{3}$Fe$_{5}$O$_{12}$, YIG) using a common ferromagnetic
+metal (permalloy, Py) as a magnetic control gate. A Py electrode, placed
+between two Pt injector and detector electrodes, acts as a magnetic gate in our
+prototypical magnon transistor device. By manipulating the magnetization
+direction of Py with respect to that of YIG, the transmission of magnons
+through the Py|YIG interface can be controlled, resulting in a modulation of
+the non-equilibrium magnon density in the YIG channel between the Pt injector
+and detector electrodes. This study opens up the possibility of using the
+magnetic gating effect for magnon-based spin logic applications.",1909.03775v1
+2019-09-11,Determining key spin-orbitronic parameters by means of propagating spin waves,"We characterize spin wave propagation and its modification by an electrical
+current in Permalloy(Py)/Pt bilayers with Py thickness between 4 and 20 nm.
+First, we analyze the frequency non-reciprocity of surface spin waves and
+extract from it the interfacial Dzyaloshinskii-Moriya interaction constant
+$D_s$ accounting for an additional contribution due to asymmetric surface
+anisotropies. Second, we measure the spin-wave relaxation rate and deduce from
+it the Py/Pt spin mixing conductance $g^{\uparrow\downarrow}_{eff}$. Last,
+applying a \textit{dc} electrical current, we extract the spin Hall
+conductivity $\sigma_{SH}$ from the change of spin wave relaxation rate due to
+the spin-Hall spin transfer torque. We obtain a consistent picture of the spin
+wave propagation data for different film thicknesses using a single set of
+parameters $D_s=0.25$ pJ/m, $g^{\uparrow\downarrow}_{eff} = 3.2\times 10^{19}$
+m$^{-2}$ and $\sigma_{SH}=4\times10^{5}$ S/m.",1909.04935v1
+2020-03-13,Experimental demonstration and analysis of random field effects in ferromagnet/antiferromagnet bilayers,"More than 30 years ago, Malozemoff (Phys. Rev. B 35, 3679 (1987))
+hypothesized that exchange interaction at the interface between a ferromagnet
+(F) and an antiferromagnet (AF) can act as an effective random field, which can
+profoundly affect the magnetic properties of the system. However, until now
+this hypothesis has not been directly experimentally tested. We utilize
+magnetoelectronic measurements to analyze the effective exchange fields at
+Permalloy/CoO interface. Our results cannot be explained in terms of
+quasi-uniform effective exchange fields, but are in agreement with the
+random-field hypothesis of Malozemoff. The presented approach opens a new route
+for the quantitative analysis of effective exchange fields and anisotropies in
+magnetic heterostructures for memory, sensing and computing applications.",2003.06295v2
+2020-06-22,Vortices in Kekulene Molecules,"Kekulene is an aromatic hydrocarbon with formula C48H24 arranged in the shape
+of a closed super-ring as shown in Fig. 2. It consists of a sublattice with 48
+C atoms with spin 5/2 and a 24 hydrogen sublattice with spin 2. In this
+communication, we use Monte Carlo simulations to determine the magnetic
+structures present in Kekulene for several temperatures (T) and dipole
+anisotropies ({\delta} = D/J). Our results show that there are two regimes at
+low temperature separated by a crossover at 2.5 < {\delta}cross < 3.0. For
+{\delta} < {\delta}cross the ground state has a unique vortex configuration. In
+the region {\delta} > {\delta}cross arrangements of vortices-antivortices
+(V-AV) appears. As temperature raises the vortex structure disorders and small
+oscillations take over. The importance on synthesizing this molecule grounds in
+the possibility of building real planar structures of sizes at least 10 times
+smaller than the earlier proposed permalloy nanodots. It is worthy to mention
+that Kekulene is a planar structure with atomic thickness, which is a great
+advantage compared with other nanomagnetic structures.",2006.12660v1
+2020-06-30,Spin-orbit torque magnetization switching in MoTe2/permalloy heterostructures,"The ability to switch magnetic elements by spin-orbit-induced torques has
+recently attracted much attention for a path towards high-performance,
+non-volatile memories with low power consumption. Realizing efficient
+spin-orbit-based switching requires harnessing both new materials and novel
+physics to obtain high charge-to-spin conversion efficiencies, thus making the
+choice of spin source crucial. Here we report the observation of spin-orbit
+torque switching in bilayers consisting of a semimetallic film of 1T'-MoTe2
+adjacent to permalloy. Deterministic switching is achieved without external
+magnetic fields at room temperature, and the switching occurs with currents one
+order of magnitude smaller than those typical in devices using the
+best-performing heavy metals. The thickness dependence can be understood if the
+interfacial spin-orbit contribution is considered in addition to the bulk spin
+Hall effect. Further threefold reduction in the switching current is
+demonstrated with resort to dumbbell-shaped magnetic elements. These findings
+foretell exciting prospects of using MoTe2 for low-power semimetal material
+based spin devices.",2006.16618v1
+2020-07-01,Magnetic asymmetry induced anomalous spin-orbit torque in IrMn,"We demonstrate an anomalous spin-orbit torque induced by the broken magnetic
+symmetry in the antiferromagnet IrMn. We study the magnetic structure of three
+phases of IrMn thin films using neutron diffraction technique. The magnetic
+mirror symmetry M' is broken laterally in both L10-IrMn and L12-IrMn3 but not
+{\gamma}-IrMn3. We observe an out-of-plane damping-like spin-orbit torque in
+both L10-IrMn/permalloy and L12-IrMn3/permalloy bilayers but not in
+{\gamma}-IrMn3/permalloy. This is consistent with both the symmetry analysis on
+the effects of a broken M' on spin-orbit torque and the theoretical predictions
+of the spin Hall effect and the Rashba-Edelstein effect. In addition, the
+measured spin-orbit torque efficiencies are 0.61+-0.01, 1.01+-0.03 and
+0.80+-0.01 for the L10, L12 and {\gamma} phases, respectively. Our work
+highlights the critical roles of the magnetic asymmetry in spin-orbit torque
+generation.",2007.00262v1
+2020-07-09,Repeated deterministic defect-assisted switching of magnetic vortex core polarity,"Because of its stability, the polarity of a magnetic vortex core (VC) is a
+candidate for binary data storage. Switching can be accomplished, e.g, by
+driving the VC above a critical velocity $v_c$. Here, we report on controlled
+and repeated switching of VC polarity by significantly reducing $v_c$ locally.
+We excite vortex dynamics in thin Permalloy disks with a magnetic field pulse,
+and map the two-dimensional VC trajectory using time-resolved Kerr microscopy.
+In pristine samples, we observe normal gyrotropic motion of the VC. After
+laser-induced generation of defects, however, we observe repeated VC reversal
+at much-reduced critical velocities as low as 20 m/s. Micromagnetic simulations
+reveal how local reduction of exchange coupling can create VC reversal sites
+for deterministic VC switching.",2007.05015v1
+2020-07-29,Tuning Spin Current Injection at Ferromagnet/Non-Magnet Interfaces by Molecular Design,"There is a growing interest in utilizing the distinctive material properties
+of organic semiconductors for spintronic applications. Here, we explore
+injection of pure spin current from Permalloy into a small molecule system
+based on dinaphtho[2,3-b:2,3-f]thieno[3,2-b]thiophene (DNTT) at ferromagnetic
+resonance. The unique tunability of organic materials by molecular design
+allows us to study the impact of interfacial properties on the spin injection
+efficiency systematically. We show that both, spin injection efficiency at the
+interface as well as the spin diffusion length can be tuned sensitively by the
+interfacial molecular structure and side chain substitution of the molecule.",2007.16068v1
+2021-01-20,Spin-current mediated exchange coupling in MgO-based magnetic tunnel junctions,"Heterostructures composed of ferromagnetic layers that are mutually
+interacting through a nonmagnetic spacer are at the core of magnetic sensor and
+memory devices. In the present study, layer-resolved ferromagnetic resonance
+was used to investigate the coupling between the magnetic layers of a
+Co/MgO/Permalloy magnetic tunnel junction. Two magnetic resonance peaks were
+observed for both magnetic layers, as probed at the Co and Ni L3 x-ray
+absorption edges, showing a strong interlayer interaction through the
+insulating MgO barrier. A theoretical model based on the
+Landau-Lifshitz-Gilbert-Slonczewski equation was developed, including exchange
+coupling and spin pumping between the magnetic layers. Fits to the experimental
+data were carried out, both with and without a spin pumping term, and the
+goodness of the fit was compared using a likelihood ratio test. This rigorous
+statistical approach provides an unambiguous proof of the existence of
+interlayer coupling mediated by spin pumping.",2101.08157v1
+2021-04-22,Theory for electrical detection of the magnon Hall effect induced by dipolar interactions,"We derive the anomalous Hall contributions arising from dipolar interactions
+to diffusive spin transport in magnetic insulators. Magnons, the carriers of
+angular momentum in these systems, are shown to have a non-zero Berry
+curvature, resulting in a measurable Hall effect. For yttrium iron garnet (YIG)
+thin films we calculate both the anomalous and magnon spin conductivities. We
+show that for a magnetic field perpendicular to the film the anomalous Hall
+conductivity is finite. This results in a non-zero Hall signal, which can be
+measured experimentally using Permalloy strips arranged like a Hall bar on top
+of the YIG thin film. We show that electrical detection and injection of spin
+is possible, by solving the resulting diffusion-relaxation equation for a Hall
+bar. We predict the experimentally measurable Hall coefficient for a range of
+temperatures and magnetic field strengths. Most strikingly, we show that there
+is a sign change of the Hall coefficient associated with increasing the
+thickness of the film.",2104.11304v1
+2021-05-12,Various facets of magnetic charge correlation: Micromagnetic and distorted waveBorn approximation simulations study,"The emergent concept of magnetic charge quasi-particle provides a new realm
+to study the evolution of magnetic properties in two-dimensional artificially
+frustrated magnets. We report on the exploration of magnetic phases due to
+various magnetic charge correlation using the complementary numerical
+techniques of micromagnetic and distorted wave Born approximation simulations
+in artificial permalloy honeycomb lattice. The honeycomb element length varies
+between 10 nm and 100 nm, while the width and thickness are kept within the
+single domain limit. In addition to the charge ordered loop state, we observe
+disordered charge arrangement, characterized by the random distribution of
+$\pm$Q charges, in single domain size honeycomb lattice. As the length of
+honeycomb element increases, low multiplicity magnetic charges tend to form
+contiguous bands in thinner lattice. Thin honeycomb lattice with 100 nm element
+length exhibits a perfect spin ice pattern, which remains unaffected to the
+modest increase in the width of element size. We simulate scattering profiles
+under the pretext of distorted wave Born approximation formalism for the
+micromagnetic phases. The results are expected to provide useful guidance in
+the experimental investigation of magnetic phases in artificial honeycomb
+magnet.",2105.05753v1
+2021-05-24,Phase-resolved electrical detection of coherently coupled magnonic devices,"We demonstrate the electrical detection of magnon-magnon hybrid dynamics in
+yttrium iron garnet/permalloy (YIG/Py) thin film bilayer devices. Direct
+microwave current injection through the conductive Py layer excites the hybrid
+dynamics consisting of the uniform mode of Py and the first standing spin wave
+($n=1$) mode of YIG, which are coupled via interfacial exchange. Both the two
+hybrid modes, with Py or YIG dominated excitations, can be detected via the
+spin rectification signals from the conductive Py layer, providing phase
+resolution of the coupled dynamics. The phase characterization is also applied
+to a nonlocally excited Py device, revealing the additional phase shift due to
+the perpendicular Oersted field. Our results provide a device platform for
+exploring hybrid magnonic dynamics and probing their phases, which are crucial
+for implementing coherent information processing with magnon excitations",2105.11057v1
+2021-08-02,Spin Wave Computing using pre-recorded magnetization patterns,"We propose a novel type of a spin wave computing device, based on a bilayer
+structure which includes a bias layer, made from a hard magnetic material and a
+propagation layer, made from a magnetic material with low damping, for example,
+Yttrium Garnet (YiG) or Permalloy. The bias layer maintains a stable
+pre-recorded magnetization pattern, generating a bias field with a desired
+spatial dependence, which in turn sets the equilibrium magnetization inside the
+propagation layer. When an external source applies an RF field or spinwave to
+the propagation layer, excited spin waves scatter on the magnetization's
+inhomogenuities, resulting in a complex interference behavior. One thus has the
+ability to adjust spin wave propagation properties simply by altering the
+magnetization in the bias layer. We demonstrate that the phenomenon can be
+utilized to perform a variety of computational operations, including Fourier
+Transform, Vector-Matrix multiplication and Grover search algorithm, with the
+operational parameters exceeding conventional designs by orders of magnitude.",2108.00909v1
+2021-10-25,Femtosecond laser comb driven perpendicular standing spin waves,"We study femtosecond laser comb driven sustained and coherent spin wave (SW)
+generation in permalloy (Py) films over a thickness range of $d =$ 40--100 nm.
+A simple rapid demagnetization model describes the dependence of the observed
+SW intensity on laser power for all film thicknesses. In the thicker films we
+observe laser comb excited perpendicular standing spin waves up to third order
+and to 18 multiples of the 1 GHz laser repetition rate. Our results demonstrate
+the versatility of femtosecond combs as contact-less SW point sources over a
+wide range of film thickness and type of SW modes.",2110.12947v1
+2021-11-04,Mechanism of magnetic diode in artificial honeycomb lattice,"Spin diode is important prerequisite to practical manifestation of spin
+electronics. Yet, a functioning magnetic diode at room temperature is still
+illusive. Here, we reveal diode-type phenomena due to magnetic charge mediated
+conduction in artificial honeycomb geometry, made of concave shape single
+domain permalloy element. We find that honeycomb lattice defies symmetry by
+populating vertices with low and high multiplicity magnetic charges, causing
+asymmetric magnetization, in applied current of opposite polarity. High
+multiplicity units create highly resistive network, thereby inhibiting magnetic
+charge dynamics propelled electrical conduction. However, practical realization
+of this effect requires modest demagnetization factor in constituting element.
+Concave structure fulfills the condition. Subsequently, magnetic diode behavior
+emerges across broad thermal range of $T$ = 40K - 300K. The finding is a
+departure from the prevailing notion of spin-charge interaction as the sole
+guiding principle behind spintronics. Consequently, a new vista, mediated by
+magnetic charge interaction, is envisaged for spintronic research",2111.02929v3
+2021-11-15,Nonstanding spin waves in a single rectangular permalloy microstrip under uniform magnetic excitation,"Ferromagnetic resonance modes in a single rectangular Ni$_{80}$Fe$_{20}$
+microstrip were directly imaged using time-resolved scanning transmission x-ray
+microscopy combined with a phase-locked ferromagnetic resonance excitation
+scheme and the findings were corroborated by micromagnetic simulations.
+Although under uniform excitation in a single confined microstructure typically
+standing spin waves are expected, all imaged spin waves showed a nonstanding
+character both, at and off resonance, the latter being additionally detected
+with microantenna-based ferromagnetic resonance. The effect of the edge quality
+on the spin waves was observed in micromagnetic simulations.",2111.07773v3
+2022-01-21,Eigenmodes of twisted spin-waves in a thick ferromagnetic nanodisk,"Magnetic vortex is topologically nontrivial and commonly found in
+ferromagnetic nanodisks. So far, three classes spin-wave eigenmodes, i.e.,
+gyrotropic, azimuthal and radial modes, have been identified in ferromagnetic
+nanodisks. Here, using micromagnetic simulation and analytical calculation, we
+reveal twisted spin-wave modes in a thick permalloy (Ni0.8Fe0.2) nanodisk. The
+twisted spin-waves carry topological charges, which sign depends on the core
+polarity of the magnetic vortex in the nanodisk. By applying rotating magnetic
+fields at one end of the sample, we observe continuous generation of twisted
+spin-waves that have characteristic spiral phase front and carry topological
+charge l = 1, -1, 2 and -2. The dispersion relation of twisted spin-waves is
+derived analytically and the result is in good agreement with micromagnetic
+numerical calculations.",2201.08621v1
+2022-01-26,Local ferromagnetic resonance measurements of mesoscopically patterned ferromagnets using deterministically placed nanodiamonds,"Nitrogen-vacancy centers in diamond have recently been established as
+effective sensors of the magnetization dynamics in vicinal ferromagnetic
+materials. We demonstrate sub-100 nm placement accuracy of
+nitrogen-vacancy-containing nanodiamonds and use these as local sensors that
+probe optically detected ferromagnetic resonance in mesoscopically patterned
+Permalloy islands. These measurements reveal variations in the ferromagnetic
+resonance signal at different sites on these structures with distinct behavior
+in the edge and the bulk of patterned features. These test measurements
+establish an easily implemented approach for spatially targeted measurements of
+spin dynamics in mesoscale ferromagnets. In principle, the methodology can also
+be extended to local studies of nanoscale ferromagnets such as single magnetic
+nanowires and nanoparticles.",2201.10722v1
+2022-05-13,Micromagnetics of magnetic chemical modulations in soft-magnetic cylindrical nanowires,"We analyze the micromagnetics of short longitudinal modulations of a
+high-magnetization material in cylindrical nanowires made of a soft-magnetic
+material of lower magnetization such as permalloy, combining magnetic
+microscopy, analytical modeling, and micromagnetic simulations. The mismatch of
+magnetization induces curling of magnetization around the axis in the
+modulations, in an attempt to screen the interfacial magnetic charges. The
+curling angle increases with modulation length, until a plateau is reached with
+nearly full charge screening for a specific length scale~$\Delta_\mathrm{mod}$,
+larger than the dipolar exchange length of any of the two materials. The
+curling circulation can be switched by the Oersted field arising from a charge
+current with typical magnitude $10^{12} A/m^{2}$ for a diameter of $\sim$100
+nm, and reaching a maximum for $\Delta_\mathrm{mod}$.",2205.06705v2
+2022-06-28,Collective ferromagnetism of artificial square spin ice,"We have studied the temperature and magnetic field dependence of the total
+magnetic moment of large-area permalloy artificial square spin ice arrays. The
+temperature dependence and hysteresis behavior are consistent with the coherent
+magnetization reversal expected in the Stoner-Wohlfarth model, with clear
+deviations due to inter-island interactions at small lattice spacing. Through
+micromagnetic simulations, we explore this behavior and demonstrate that the
+deviations result from increasingly complex magnetization reversal at small
+lattice spacing, induced by inter-island interactions, and depending critically
+on details of the island shapes. These results establish new means to tune the
+physical properties of artificial spin ice structures and other interacting
+nanomagnet systems, such as patterned magnetic media.",2206.14147v1
+2022-08-10,Efficient spin-to-charge interconversion in Weyl semimetal TaP at room temperature,"In this paper we present spin-to-charge current conversion properties in the
+Weyl semimetal TaP by means of the inverse Rashba-Edelstein effect (IREE) with
+the integration of this quantum material with the ferromagnetic metal Permalloy
+$(Py=Ni_{81}Fe_{19})$. The spin currents are generated in the Py layer by the
+spin pumping effect (SPE) from microwave-driven ferromagnetic resonance and are
+detected by a dc voltage along the TaP crystal, at room temperature. We observe
+a field-symmetric voltage signal without the contamination of asymmetrical
+lines due to spin rectification effects observed in studies using metallic
+ferromagnets. The observed voltage is attributed to spin-to-charge current
+conversion based on the IREE, made possible by the spin-orbit coupling induced
+intrinsically by the bulk band structure of Weyl semimetals. The measured IREE
+coefficient ${\lambda}_{IREE}=(0.30 \pm{0.01})$ nm is two orders of magnitude
+larger than in graphene and is comparable to or larger than the values reported
+for some metallic interfaces and for several topological insulators.",2208.05151v1
+2022-09-23,Mapping AC Susceptibility with Quantum Diamond Microscope,"We present a novel technique for determining the microscale AC susceptibility
+of magnetic materials. We use magnetic field sensing properties of
+nitrogen-vacancy (\ce{NV-}) centers in diamond to gather quantitative data
+about the magnetic state of the magnetic material under investigation. In order
+to achieve the requisite speed in imaging, a lock-in camera is used to perform
+pixel-by-pixel lock-in detection of \ce{NV-} photo-luminescence. In addition, a
+secondary sensor is employed to isolate the effect of the excitation field from
+fields arising from magnetic structures on \ce{NV-} centers. We demonstrate our
+experimental technique by measuring the AC susceptibility of soft permalloy
+micro-magnets at excitation frequencies of up to \SI{20}{\hertz} with a spatial
+resolution of \SI{1.2}{\micro \meter} and a field of view of \SI{100}{\um}. Our
+work paves the way for microscopic measurement of AC susceptibilities of
+magnetic materials relevant to physical, biological, and material sciences.",2209.11610v1
+2022-10-04,The spin-flop transition in the quasi two dimensional antiferromagnet MnPS3 detected via thermally generated magnon transport,"We present the detection of the spin-flop transition in the antiferromagnetic
+van der Waals material MnPS3 via thermally generated nonlocal magnon transport
+using permalloy detector strips. The inverse anomalous spin Hall effect has the
+unique power to detect an out-of-plane spin accumulation which enables us to
+detect magnons with an out-of-plane spin polarization; in contrast to strips of
+high spin-orbit material such as Pt which only possess the spin Hall effect and
+are only sensitive to an in-plane spin polarization of the spin accumulation.
+We show that nonlocal magnon transport is able to measure the spin-flop
+transition in the absence of other spurious effects. Our measurements show the
+detection of magnons generated by the spin Seebeck effect before and after the
+spin-flop transition where the signal reversal of the magnon spin accumulation
+agrees with the OOP spin polarization carried by magnon modes before and after
+the SF transition.",2210.01418v1
+2022-10-13,Effect of interfaces on supercurrent through ferromagnetic materials,"Ferromagnetic Josephson junctions exhibit fascinating physics and the
+potential for applications in superconducting logic and memory. The junctions
+in a demonstrated superconducting memory prototype contain a magnetic
+spin-valve structure with Ni as the fixed layer and NiFe (Permalloy) as the
+free layer. However, NiFe exhibits poor supercurrent transmission, which limits
+the efficiency of the Josephson junction. We have previously shown that the
+supercurrent transmission through a Cu/NiFe/Cu trilayer can be improved by
+adding thin layers of Ni between the Cu and NiFe -- possibly due to the
+advantageous spin-dependent transport properties of the Cu/Ni interfaces. In
+this work we explore this idea further by replacing the Cu/NiFe interfaces with
+Pd/NiFe, which also have more desirable transport properties. Compared to the
+reference junctions containing Cu/NiFe interfaces, the new junctions exhibit an
+increase in the $\pi$-state supercurrent by a factor of 2 along with a change
+in the position of the first $0-\pi$ transition.",2210.07151v2
+2023-03-09,Phase-resolved optical characterization of nanoscale spin waves,"We study theoretically and experimentally the process of Brillouin light
+scattering on an array of silicon disks on a thin Permalloy layer. We show that
+phase-resolved Brillouin light scattering microscopy performed on an array of
+weakly interacting dielectric nanoresonators can detect nanoscale waves and
+measure their dispersion. In our experiment, we were able to map the evolution
+of the phase of the spin wave with a wavelength of 209 nm with a precision of 6
+nm. These results demonstrate the feasibility of all-optical phase-resolved
+characterization of nanoscale spin waves.",2303.05339v1
+2023-04-07,A two-color dual-comb system for time-resolved measurements of ultrafast magnetization dynamics using triggerless asynchronous optical sampling,"We report on an Er-doped fiber (EDF)-laser-based dual-comb system that allows
+us to perform triggerless asynchronous optical sampling (ASOPS) pump-probe
+measurements of ultrafast demagnetization and spin precession in magnetic
+materials. Because the oscillation frequencies of the two frequency-comb light
+sources are highly stabilized, the pulse-to-pulse timing jitter is sufficiently
+suppressed and data accumulation without any trigger signals is possible. To
+effectively induce spin precession in ferromagnetic thin films, the spectral
+bandwidth of the output of one of the EDF frequency comb sources is broadened
+by a highly nonlinear fiber and then amplified at a wavelength of about 1030 nm
+by a Yb-doped fiber amplifier. The output of the other frequency comb source is
+converted to about 775 nm by second harmonic generation. We used this system to
+observe the ultrafast demagnetization and spin precession dynamics on the
+picosecond and nanosecond time scales in a permalloy thin film. This
+time-domain spectroscopy system is promising for the rapid characterization of
+spin-wave generation and propagation dynamics in magnetic materials.",2304.03666v1
+2023-04-28,Competing signatures of intersite and interlayer spin transfer in the ultrafast magnetization dynamics,"Optically driven intersite and interlayer spin transfer are individually
+known as the fastest processes for manipulating the spin order of magnetic
+materials on the sub 100 fs time scale. However, their competing influence on
+the ultrafast magnetization dynamics remains unexplored. In our work, we show
+that optically induced intersite spin transfer (also known as OISTR) dominates
+the ultrafast magnetization dynamics of ferromagnetic alloys such as Permalloy
+(Ni80Fe20) only in the absence of interlayer spin transfer into a substrate.
+Once interlayer spin transfer is possible, the influence of OISTR is
+significantly reduced and interlayer spin transfer dominates the ultrafast
+magnetization dynamics. This provides a new approach to control the
+magnetization dynamics of alloys on extremely short time scales by fine-tuning
+the interlayer spin transfer.",2304.14957v1
+2023-04-29,Magnetization precession after non-collinear dual optical excitation,"We investigate the impact of non-collinear dual optical excitation on the
+magnetization precession in a permalloy thin film using two ultrashort laser
+pulses. By analyzing the magnetization dynamics using time-resolved
+magneto-optical methods, we find that the excitation with two ultrashort
+optical pulses introduces a long-lasting modification of the electron system
+seen as a sizable decrease of the precession frequency and significant increase
+(about 25%) of the decay time. Our results reveal that the observed effect
+strongly depends on the respective polarization of the two excitation pulses
+and the time delay between two optical pulses. Our findings indicate the
+occurrence of a new nonlinear opto-spin effect during photoexcitation with two
+interfering optical pulses which can potentially be observed in various
+materials and at different photon wavelengths.",2305.00259v2
+2023-05-01,Coherent and incoherent magnons induced by strong ultrafast demagnetization in thin permalloy films,"Understanding spin dynamics on femto- and picosecond timescales offers new
+opportunities for faster and more efficient spintronic devices. Here, we
+experimentally investigate the coherent spin dynamics after ultrashort laser
+excitation by time-resolved magneto optical Kerr effect (TR-MOKE) in thin
+Ni80Fe20 films. We provide a detailed study of the magnetic field and pump
+fluence dependence of the coherent precessional dynamics. We show that the
+coherent precession lifetime increases with the applied external magnetic field
+which cannot be understood by viscous Gilbert damping of the coherent magnons.
+Instead, it can be explained by nonlinear magnon interactions and by the change
+in the fraction of incoherent magnons. This interpretation is in agreement with
+the observed trends of the coherent magnon amplitude and lifetime as a function
+of the exciting laser fluence. Our results provide a new insight into the
+magnetization relaxation processes in ferromagnetic thin films, which is of
+great importance for further spintronic applications.",2305.00814v2
+2023-05-13,Suhl Instabilities in Nanoscopic Spheroids,"We simulate the magnetization dynamics of a permalloy spheroid of nanoscopic
+size in zero external field, such that both dipolar and exchange interactions
+are important. Low excitation power is used to obtain the frequencies and mode
+patterns of many normal modes. At higher power, non-linear three and four mode
+couplings between magnons carrying orbital angular momentum are observed to
+give rise to Suhl instabilities. Suhl's analysis of the selection rules
+governing the allowed processes is extended to initial states other than
+uniform precession. These rules are studied and confirmed by the simulations.
+Both down- and up-conversion are seen as well as three and four-mode processes.
+General trends are inferred for preferred instabilities among those that are
+allowed, although the thresholds for some instabilities appear to be very high.",2305.07986v1
+2023-06-24,Magnon confinement in an all-on-chip YIG cavity resonator using hybrid YIG/Py magnon barriers,"Confining magnons in cavities can introduce new functionalities to magnonic
+devices, enabling future magnonic structures to emulate established photonic
+and electronic components. As a proof-of-concept, we report magnon confinement
+in a lithographically defined all-on-chip YIG cavity created between two
+YIG/Permalloy bilayers. We take advantage of the modified magnetic properties
+of covered/uncovered YIG film to define on-chip distinct regions with
+boundaries capable of confining magnons. We confirm this by measuring multiple
+spin pumping voltage peaks in a 400 nm wide platinum strip placed along the
+center of the cavity. These peaks coincide with multiple spin-wave resonance
+modes calculated for a YIG slab with the corresponding geometry. The
+fabrication of micrometer-sized YIG cavities following this technique
+represents a new approach to control coherent magnons, while the spin pumping
+voltage in a nanometer-sized Pt strip demonstrates to be a non-invasive local
+detector of the magnon resonance intensity.",2306.14029v2
+2023-07-04,Electrically-controlled hybrid superconductor-ferromagnet cell for high density cryogenic memory,"We report the fabrication and testing, at 4.2 K, of an SISFS device, where S,
+F, and I denote a superconductor (Nb), a ferromagnetic material (permalloy),
+and an insulator (AlOx), respectively. The F layer covers about one half of the
+top electrode of the SIS Josephson junction and is positioned off-center.
+Electric current, I _tr, along the S electrode can change the magnetization of
+the F layer in such a way that, for one direction of I_tr, a magnetic flux
+penetrates the junction perpendicular to the layers, whereas for the opposite
+direction, the perpendicular magnetic flux can be removed. In the former state,
+the modulation pattern of the Josephson critical current, Ic, in the magnetic
+field, H, may acquire minimum near H=0, and restores its usual shape with
+maximum in the second state. These states can be used for building a compact
+cryogenic memory compatible with single flux quantum electronics.",2307.01433v1
+2023-07-29,Single-spin spectroscopy of spontaneous and phase-locked spin torque oscillator dynamics,"We employ N-$V$ magnetometry to measure the stray field dynamics of a
+ferromagnetic permalloy nanowire driven by spin-orbit torques. Specifically, we
+observe the optically detected magnetic resonance (ODMR) signatures of both
+spontaneous DC-driven magnetic oscillations and phase-locking to a second
+harmonic drive, developing a simple macrospin model that captures the salient
+features. We also observe signatures of dynamics beyond the macrospin model,
+including an additional ODMR feature (associated with a second SW mode) and one
+mode sapping power from another. Our results provide additional insight into
+N-$V$-spin wave coupling mechanisms, and represent a new modality for
+sub-wavelength N-$V$ scanned probe microscopy of nanoscale magnetic
+oscillators.",2307.16049v1
+2023-08-22,Observation of Current-induced Nonlinear Spin Polarization in Pt-Py Bilayers,"We experimentally observe nonlinear spin polarization in metallic bilayers of
+platinum and permalloy by means of spin-torque ferromagnetic resonance (ST-FMR)
+with the spin-Hall effects. The ST-FMR results under massive dc current
+injection contain striking features, which are not caused by extrinsic Joule
+heating, but by intrinsic nonlinear spin polarization. The emergence of
+nonlinear spin polarization is consistent with observation of unidirectional
+spin-Hall magnetoresistance due to magnon generation/annihilation. Moreover,
+the magnon generation (annihilation) leads to effective magnetization shrinkage
+(expansion) revealed by the ST-FMR measurements. The present study paves a way
+to spin-Hall effect based nonlinear spintronic devices as well as
+6th-generation mobile communication light sources.",2308.11156v2
+2023-11-19,Unraveling oscillations at ferro(para)magnetic and non-collinear antiferromagnetic interfaces,"Here, we show that the ferro(para)magnetic and non-collinear
+antiferromagnetic interfaces contribute to oscillating signals observed in the
+magnetoresistance. We associate the effect with the fact that the spins on the
+surface of IrMn3 produce instability in the surface magnetoresistance of the
+material, which is sensitive to the magnetic field. We carried out experiments
+using bilayers of IrMn3 under permalloy (Py) and IrMn3 under platinum (Pt). The
+oscillations were intensely evident at the Py/IrMn3 interface and less explicit
+at the Pt/IrMn3 interface. We carried out the experiments using pulsed current,
+with a square pulse width of 1{\mu}s and amplitudes of 20 {\mu}A to 20 mA. The
+oscillating signals are proportional to the crystallographic direction of the
+material, the ferromagnetism of the material adjacent to IrMn3, and sensitive
+to the amplitude of the pulsed current. We believe that observation is a way of
+transmitting encoded information through magnetoresistance.",2311.11401v1
+2024-03-25,Detection of spin pumping free of rectification and thermal artefacts in molecular-based ferromagnetic insulator V[TCNE]x~2,"The molecular-based ferrimagnetic insulator V(TCNE)x has gained recent
+interest for efficient spin-wave excitation due to its low Gilbert damping
+ratio a=4E-5, and narrow ferromagnetic resonance linewidth f=1Oe. Here we
+report a clean spin pumping signal detected on V(TCNE)x/metal bilayer
+structures, free from spin rectification or thermal artifacts. On-chip coupling
+of microwave power is achieved via a coplanar waveguide to measure the in-plane
+angle-dependence of the inverse spin-Hall effect under ferromagnetic resonance
+conditions with respect to a constant external magnetic field. A signature of
+pure spin current from V(TCNE)x is observed in both platinum and permalloy
+metal layers, demonstrating the utility of V(TCNE)x for magnon spintronics
+studies in molecule/solid-state heterostructures.",2403.16429v2
+2024-04-04,Direct visualization of local magnetic domain dynamics in a 2D Van der Walls material/ferromagnet interface,"Exploring new strategies for controlling the magnetic domain propagation is
+the key to realize ultrafast, high-density domain wall-based memory and logic
+devices for next generation computing. These strategies include strain
+modulation in multiferroic devices, geometric confinement and area-selective
+pinning of domain wall. 2D Van der Waals materials introduce localized
+modifications to the interfacial magnetic order, enabling control over the
+propagation of magnetic domains. Here, using Lorentz-Transmission Electron
+Microscopy (L-TEM) along with the Modified Transport of Intensity equations
+(MTIE), we demonstrate controlled domain expansion with in-situ magnetic field
+in a ferromagnet (Permalloy, NiFe) interfacing with a 2D Van der Waals material
+Graphene (Gr). The Gr/NiFe interface exhibits distinctive domain expansion rate
+with magnetic field selectively near the interface which is further analyzed
+using micromagnetic simulations. Our findings are crucial for comprehending
+direct visualization of interface controlled magnetic domain expansion,
+offering insights for developing future domain wall-based technology.",2404.03177v1
+2000-01-19,Fermi surface origin of the interrelationship between magnetocrystalline anisotropy and compositional order in transitional metal alloys,"Recently, we outlined a scheme to investigate the effects of compositional
+order on the magnetocrystalline anisotropy of alloys from a first-principles
+electronic structure point of view \{Phys. Rev. Lett. {\bf 83}, 5369 (1999)\}
+and showed that compositional order enhances the magnitude of
+magnetocrystalline anisotropy energy (MAE) of Co$_{0.5}$Pt$_{0.5}$ alloy by
+some two orders of magnitude as well as affecting the equilibrium magnetization
+direction. Here we describe our scheme in detail and present an in-depth study
+of the effect by demonstrating its Fermi surface origin. In
+Co$_{0.25}$Pt$_{0.75}$ alloy we find that the perfect $ L1_2 $ structure has a
+very small MAE whereas imposition of directional order enhances the MAE by two
+orders of magnitude. We also present the effect of lattice distortion
+(tetragonalization) on the MAE on the same footing and find that in the
+Co$_{0.5}$Pt$_{0.5}$ alloy it accounts for only about 20% of the observed MAE,
+thus confirming that compositional order is the major player in the enhancement
+of MAE. We also examine the directional chemical order that can be produced by
+magnetic annealing within the same framework. We extract a Fermi surface
+mechanism for the effect in an explicit study of permalloy. Finally, we propose
+that the Fermi surface plays a major role in the strong coupling between
+magnetocrystalline anisotropy and compositional order in many magnetic alloys.",0001271v1
+2002-04-25,Statics and Fast Dynamics of Nanomagnets with Vortex Structure,"Within the framework of the Landau-Lifshitz-Gilbert equation, using permalloy
+parameters, we study the statics and dynamics of flat circular magnetic
+nano-structures with an in-plane magnetic vortex configuration, putting
+particular emphasis on the (planar) vorticity of the magnetic state and on the
+(perpendicular) polarisation of the vortex center (which may be shifted with
+respect to the center of the circle). These binary degrees of freedom can in
+principle be used to manipulate two independent bits of information.
+  Studying switching processes induced by in-plane and out-of plane field
+pulses we find that it is possible to switch the vorticity of the magnetic dot
+on a time scale of 40 ps in strong enough and short enough perpendicular
+external field pulses (B_z^ext \approx 0.5 T, duration \approx 40 ps). But for
+realistically small values of the Gilbert damping, only the vorticity can be
+switched this fast, and it turns out that it is better to dismiss the center of
+the circle totally, concentrating on flat 'nano-rings' with an inner radius R_1
+and an outer radius R_2. On these 'nano-rings' the vortex state is more stable,
+and with respect to the switching of the vorticity these structures have
+similar properties as circular dots.",0204541v3
+2005-06-09,Magnetoresistance Anisotropy of Polycrystalline Cobalt Films: Geometrical-Size- and Domain-Effects,"The magnetoresistance (MR) of 10 nm to 200 nm thin polycrystalline Co-films,
+deposited on glass and insulating Si(100), is studied in fields up to 120 kOe,
+aligned along the three principal directions with respect to the current:
+longitudinal, transverse (in-plane), and polar (out-of-plane). At technical
+saturation, the anisotropic MR (AMR) in polar fields turns out to be up to
+twice as large as in transverse fields, which resembles the yet unexplained
+geometrical size-effect (GSE), previously reported for Ni- and Permalloy films.
+Upon increasing temperature, the polar and transverse AMR's are reduced by
+phonon-mediated sd-scattering, but their ratio, i.e. the GSE remains unchanged.
+Basing on Potters's theory [Phys.Rev.B 10, 4626(1974)], we associate the GSE
+with an anisotropic effect of the spin-orbit interaction on the sd-scattering
+of the minority spins due to a film texture. Below magnetic saturation, the
+magnitudes and signs of all three MR's depend significantly on the domain
+structures depicted by magnetic force microscopy. Based on hysteresis loops and
+taking into account the GSE within an effective medium approach, the three MR's
+are explained by the different magnetization processes in the domain states.
+These reveal the importance of in-plane uniaxial anisotropy and out-of-plane
+texture for the thinnest and thickest films, respectively.",0506232v1
+2008-06-26,Ferromagnetic resonance force spectroscopy of individual sub-micron size samples,"We review how a magnetic resonance force microscope (MRFM) can be applied to
+perform ferromagnetic resonance (FMR) spectroscopy of \emph{individual}
+sub-micron size samples. We restrict our attention to a thorough study of the
+spin-wave eigen-modes excited in permalloy (Py) disks patterned out of the same
+43.3 nm thin film. The disks have a diameter of either 1.0 or $0.5 \mu$m and
+are quasi-saturated by a perpendicularly applied magnetic field. It is shown
+that \emph{quantitative} spectroscopic information can be extracted from the
+MRFM measurements. In particular, the data are extensively compared with
+complementary approximate models of the dynamical susceptibility: i) a 2D
+analytical model, which assumes an homogeneous magnetization dynamics along the
+thickness and ii) a full 3D micromagnetic simulation, which assumes an
+homogeneous magnetization dynamics below a characteristic length scale $c$ and
+which approximates the cylindrical sample volume by a discretized
+representation with regular cubic mesh of lateral size $c=3.9$ nm. In our
+analysis, the distortions due to a breaking of the axial symmetry are taken
+into account, both models incorporating the possibility of a small misalignment
+between the applied field and the normal of the disks.",0806.4244v1
+2008-11-05,Self organized mode locking effect in superconductor / ferromagnet hybrids,"The vortex dynamics in a low temperature superconductor deposited on top of a
+rectangular array of micrometer size permalloy triangles is investigated
+experimentally. The rectangular unit cell is such that neighboring triangles
+physically touch each other along one direction. This design stabilizes
+remanent states which differ from the magnetic vortex state typical of
+individual non-interacting triangles. Magnetic Force Microscopy images have
+revealed that the magnetic landscape of the template can be switched to an
+ordered configuration after magnetizing the sample with an in-plane field. The
+ordered phase exhibits a broad flux flow regime with relatively low critical
+current and a highly anisotropic response. This behavior is caused by the
+spontaneous formation of two separated rows of vortices and antivortices along
+each line of connected triangles. The existence of a clear flux flow regime
+even for zero external field supports this interpretation. The density of
+induced vortex-antivortex pairs is directly obtained using a high frequency
+measurement technique which allows us to resolve the discrete motion of
+vortices. Strikingly, the presence of vortex-antivortex rows gives rise to a
+self organized synchronized motion of vortices which manifests itself as field
+independent Shapiro steps in the current-voltage characteristics.",0811.0798v1
+2009-02-15,Sudden Critical Current Drops Induced in S/F Structures,"In the search for new physical properties of S/F structures, we have found
+that the superconductor critical current can be controlled by the domain state
+of the neighboring ferromagnet. The superconductor is a thin wire of thickness
+d_{s} ~ 2 xi_{S}. Nb/Co and Nb/Py (Permalloy Ni_{80}Fe_{20}) bilayer structures
+were grown with a significant magnetic anisotropy. Critical current
+measurements of Nb/Co structures with ferromagnet thickness d_{F} > 30nm show
+sudden drops in two very defined steps when the measurements are made along the
+hard axes direction (i.e. current track parallel to hard anisotropy axes
+direction). These drops disappear when they are made along the easy axis
+direction or when the ferromagnet thickness is below 30nm. The drops are
+accompanied by vortex flux flow. In addition magnetorestistance measurements
+close to Tc show a sharp increase near saturation fields of the ferromagnet.
+Similar results are reproduced in Nb/Py bilayer structure with the ferromagnet
+thickness d_{F} ~ 50nm along the easy anisotropy axes. These results are
+explained as being due to spontaneous vortex formation and flow induced by
+Bloch domain walls of the ferromagnet underneath. We argue these Bloch domain
+walls produce a 2D vortex-antivortex lattice structure.",0902.2572v2
+2009-08-30,Measurement of spin memory lengths in PdNi and PdFe ferromagnetic alloys,"Weakly ferromagnetic alloys are being used by several groups in the study of
+superconducting/ferromagnetic hybrid systems. Because spin-flip and spin-orbit
+scattering in such alloys disrupt the penetration of pair correlations into the
+ferromagnetic material, it is desirable to have a direct measurement of the
+spin memory length in such alloys. We have measured the spin memory length at
+4.2 K in sputtered Pd0.88Ni0.12 and Pd0.987Fe0.013 alloys using methods based
+on current-perpendicular-to-plane giant magnetoresistance. The alloys are
+incorporated into hybrid spin valves of various types, and the spin memory
+length is determined by fits of the Valet-Fert spin-transport equations to data
+of magnetoresistance vs. alloy thickness. For the case of PdNi alloy, the
+resulting values of the spin memory length are lsf(PdNi) = 2.8 +/- 0.5 nm and
+5.4 +/- 0.6 nm, depending on whether or not the PdNi is exchange biased by an
+adjacent Permalloy layer. For PdFe, the spin memory length is somewhat longer,
+lsf(PdFe) = 9.6 +/- 2 nm, consistent with earlier measurements indicating lower
+spin-orbit scattering in that material. Unfortunately, even the longer spin
+memory length in PdFe may not be long enough to facilitate observation of
+spin-triplet superconducting correlations predicted to occur in
+superconducting/ferromagnetic hybrid systems in the presence of magnetic
+inhomogeneity.",0908.4375v1
+2010-04-09,Thermally driven spin injection from a ferromagnet into a non-magnetic metal,"Creating, manipulating and detecting spin polarized carriers are the key
+elements of spin based electronics. Most practical devices use a perpendicular
+geometry in which the spin currents, describing the transport of spin angular
+momentum, are accompanied by charge currents. In recent years, new sources of
+pure spin currents, i.e., without charge currents, have been demonstrated and
+applied. In this paper, we demonstrate a conceptually new source of pure spin
+current driven by the flow of heat across a ferromagnetic/non-magnetic metal
+(FM/NM) interface. This spin current is generated because the Seebeck
+coefficient, which describes the generation of a voltage as a result of a
+temperature gradient, is spin dependent in a ferromagnet. For a detailed study
+of this new source of spins, it is measured in a non-local lateral geometry. We
+developed a 3D model that describes the heat, charge and spin transport in this
+geometry which allows us to quantify this process. We obtain a spin Seebeck
+coefficient for Permalloy of -3.8 microvolt/Kelvin demonstrating that thermally
+driven spin injection is a feasible alternative for electrical spin injection
+in, for example, spin transfer torque experiments.",1004.1566v1
+2011-03-30,Magnetic domain-wall velocity enhancement induced by a transverse magnetic field,"Spin dynamics of field-driven domain walls (DWs) guided by Permalloy
+nanowires are studied by high-speed magneto-optic polarimetry and numerical
+simulations. DW velocities and spin configurations are determined as functions
+of longitudinal drive field, transverse bias field, and nanowire width.
+Nanowires having cross-sectional dimensions large enough to support vortex wall
+structures exhibit regions of drive-field strength (at zero bias field) that
+have enhanced DW velocity resulting from coupled vortex structures that
+suppress oscillatory motion. Factor of ten enhancements of the DW velocity are
+observed above the critical longitudinal drive-field (that marks the onset of
+oscillatory DW motion) when a transverse bias field is applied. Nanowires
+having smaller cross-sectional dimensions that support transverse wall
+structures also exhibit a region of higher mobility above the critical field,
+and similar transverse-field induced velocity enhancement but with a smaller
+enhancement factor. The bias-field enhancement of DW velocity is explained by
+numerical simulations of the spin distribution and dynamics within the
+propagating DW that reveal dynamic stabilization of coupled vortex structures
+and suppression of oscillatory motion in the nanowire conduit resulting in
+uniform DW motion at high speed.",1103.6056v1
+2011-09-30,Cooling and heating with electron spins: Observation of the spin Peltier effect,"The Peltier coefficient describes the amount of heat that is carried by an
+electrical current when it passes through a material. Connecting two materials
+with different Peltier coefficients causes a net heat flow towards or away from
+the interface, resulting in cooling or heating at the interface - the Peltier
+effect. Spintronics describes the transport of charge and angular momentum by
+making use of separate spin-up and spin-down channels. Recently, the merger of
+thermoelectricity with spintronics has given rise to a novel and rich research
+field named spin caloritronics. Here, we report the first direct experimental
+observation of refrigeration/heating driven by a spin current, a new spin
+thermoelectric effect which we call the spin Peltier effect. The heat flow is
+generated by the spin dependency of the Peltier coefficient inside the
+ferromagnetic material. We explored the effect in a specifically designed spin
+valve pillar structure by measuring the temperature using an electrically
+isolated thermocouple. The difference in heat flow between the two magnetic
+configurations leads to a change in temperature. With the help of 3-D finite
+element modeling, we extracted permalloy spin Peltier coefficients in the range
+of -0.9 to -1.3 mV. These results enable magnetic control of heat flow and
+provide new functionality for future spintronic devices.",1109.6898v1
+2011-12-08,200 ps Vortex Core Reversal by Azimuthal Spin Waves,"Spin wave mediated vortex core reversal has been investigated by
+time-resolved scanning transmission X-ray microscopy (STXM). Movies showing the
+development of the spin wave and vortex core magnetization dynamics during
+unidirectional vortex core reversal could be taken in Permalloy discs, 1.6 \mu
+m in diameter and 50 nm thick, during excitation with rotating ac field bursts
+of one period duration at 4.5 GHz and with amplitudes up to 4 mT.
+Unidirectional switching is achieved by taking advantage of an asymmetry for CW
+or CCW excitation caused by the gyrofield. The differences in the magnetization
+dynamics due to this asymmetry could be imaged during continuous excitation
+with multi-GHz rotating fields. All our experimental results are in good
+agreement with micromagnetic simulations.
+  In addition, for the sample geometry given above, simulations reveal a lower
+limit of about 200 ps for the time of unidirectional vortex core switching,
+which cannot be overcome by shortening the excitation length or by increasing
+the excitation amplitude. We explain this limitation by the finite time needed
+for an energy transfer of the global excitation towards the center of the
+sample. Thus smaller samples will allow for much shorter vortex core reversal
+times.",1112.1903v1
+2012-06-07,Anisotropic magnetothermoelectric power of ferromagnetic thin films,"We compare the behavior of the magnetothermoelectric power (MTEP)in metallic
+ferromagnetic thin films of Ni80Fe20 (Permalloy; Py), Co and CrO2 at
+temperatures in the range of 100 K to 400 K. In 25 nm thick Py films and 50 nm
+thick Co films both the anisotropic magnetoresistance (AMR) and MTEP show a
+relative change in resistance and thermoelectric power (TEP) of the order of
+0.2% when the magnetic field is reversed, and in both cases there is no
+significant change in AMR or MTEP any more after the saturation field has been
+reached. Surprisingly, both Py and Co films have opposite MTEP behavior
+although both have the same sign for AMR and TEP. The data on 100 nm films of
+fully spin-polarized CrO2, grown both on TiO2 and on sapphire, show a different
+picture. The MTEP behavior at low fields shows peaks similar to the AMR in
+these films, with variations up to 1%. With increasing field both the MR and
+the MTEP variations keeps growing, with MTEP showing relative changes of 1.5%
+with the thermal gradient along the b-axis and even 20% with the gradient along
+the c-axis, with an intermediate value of 3% for the film on sapphire. It
+appears that the low-field effects are due to magnetic domain switching, while
+the high-field effects are intrinsic to the electronic structure of CrO2.",1206.1527v2
+2013-05-04,Effect of perpendicular uniaxial anisotropy on the annihilation fields of magnetic vortices,"The magnetic vortex structure, that is present in several nanoscopic systems,
+is stable and can be manipulated through the application of a magnetic field or
+a spin polarized current. The size and shape of the core are strongly affected
+by the anisotropy, however its role on the core behavior has not yet been
+clarified. In the present work we investigate the influence of a perpendicular
+anisotropy on the annihilation and shape of magnetic vortex cores in permalloy
+disks. We have used both micromagnetic simulations with the OOMMF code, and an
+analytical model that assumes that the shape of the core does not change during
+the hysteresis cycle, known as the rigid core model, to calculate the
+annihilation fields. In both cases we found that the annihilation fields
+decrease with increasing perpendicular anisotropy for almost all the structures
+investigated. The simulations show that for increasing anisotropy or dot
+thickness, or both, the vortex core profile changes its shape, becoming
+elongated. For every dot thickness, this change does not depend on the dot
+radius, but on the relative distance of the core from the center of the dot.",1305.0942v2
+2013-10-28,Precise determination of the spectroscopic g-factor using broadband ferromagnetic resonance spectroscopy,"We demonstrate that the spectroscopic g-factor can be determined with high
+precision and accuracy by broadband ferromagnetic resonance measurements and
+applying an asymptotic analysis to the data. Spectroscopic data used to
+determine the g-factor is always obtained over a finite range of frequencies,
+which can result in significant errors in the fitted values of the
+spectroscopic g-factor. We show that by applying an asymptotic analysis to
+broadband datasets, precise values of the intrinsic g-factor can be determined
+with errors well below 1 %, even when the exact form of the Kittel equation
+(which describes the relationship between the frequency and resonance field) is
+unknown. We demonstrate this methodology with measured data obtained for
+sputtered Ni80Fe20 (""Permalloy"") thin films of varied thicknesses, where we
+determine the bulk g-factor value to be 2.109 +/- 0.003. Such an approach is
+further validated by application to simulated data that includes both noise and
+an anisotropy that is not included in the Kittel equation that was used in the
+analysis. Finally, we show a correlation of thickness and interface structure
+to the magnitude of the asymptotic behavior, which provide insight into
+additional mechanisms that may induce deviations from the Kittel equation.",1310.7515v1
+2015-12-07,Current Driven Domain Wall Depinning in Notched Permalloy Nanowires,"In this work, we have investigated the domain wall (DW) depinning behavior in
+the notched nanowire by a micromagnetic simulation. A transverse domain wall
+(TW) was initially positioned at the center of notch and 1 ns length current
+pulse was applied to depin the DW with respect to the notch size s and the wire
+width variation. We have observed the depinning current density Jd which was a
+minimum current to escape DW from the notch. It was found that the depinning
+current density decreased as the wire width and the notch size increased. In
+the depinning process, we observed the inner structure of DW generally
+transformed from TW to anti-vortex wall (AVW). Interestingly, for the case of s
+less than 70 nm, AVW formed and depinned closely to the period when current
+pulse was active, while for s larger than 70 nm, AVW formed until the current
+pulse went to zero and then depinned after flipped TW was formed. It can be
+explained that the transformation of DW inner structures were affected by the
+spin torque energy and contributed to DW depinning behavior from the notched
+nanowires.",1512.01954v1
+2016-01-21,Detection of spin pumping from YIG by spin-charge conversion in a Au/Ni$_{80}$Fe$_{20}$ spin-valve structure,"Many experiments have shown the detection of spin-currents driven by
+radio-frequency spin pumping from yttrium iron garnet (YIG), by making use of
+the inverse spin-Hall effect, which is present in materials with strong
+spin-orbit coupling, such as Pt. Here we show that it is also possible to
+directly detect the resonance-driven spin-current using Au/permalloy (Py,
+Ni$_{80}$Fe$_{20}$) devices, where Py is used as a detector for the spins
+pumped across the YIG/Au interface. This detection mechanism is equivalent to
+the spin-current detection in metallic non-local spin-valve devices. By finite
+element modeling we compare the pumped spin-current from a reference Pt strip
+with the detected signals from the Au/Py devices. We find that for one series
+of Au/Py devices the calculated spin pumping signals mostly match the
+measurements, within 20%, whereas for a second series of devices additional
+signals are present which are up to a factor 10 higher than the calculated
+signals from spin pumping. We also identify contributions from thermoelectric
+effects caused by the resonant (spin-related) and non-resonant heating of the
+YIG. Thermocouples are used to investigate the presence of these thermal
+effects and to quantify the magnitude of the Spin-(dependent-)Seebeck effect.
+Several additional features are observed, which are also discussed.",1601.05605v1
+2016-07-22,Magnetic diffuse scattering in artificial kagome spin ice,"The study of magnetic correlations in dipolar-coupled nanomagnet systems with
+synchrotron x-ray scattering provides a means to uncover emergent phenomena and
+exotic phases, in particular in systems with thermally active magnetic moments.
+From the diffuse signal of soft x-ray resonant magnetic scattering, we have
+measured magnetic correlations in a highly dynamic artificial kagome spin ice
+with sub-70-nm Permalloy nanomagnets. On comparing experimental scattering
+patterns with Monte Carlo simulations based on a needle-dipole model, we
+conclude that kagome ice I phase correlations exist in our experimental system
+even in the presence of moment fluctuations, which is analogous to bulk spin
+ice and spin liquid behavior. In addition, we describe the emergence of
+quasi-pinch-points in the magnetic diffuse scattering in the kagome ice I
+phase. These quasi-pinch-points bear similarities to the fully developed pinch
+points with singularities of a magnetic Coulomb phase, and continually evolve
+into the latter on lowering the temperature. The possibility to measure
+magnetic diffuse scattering with soft x rays opens the way to study magnetic
+correlations in a variety of nanomagnetic systems.",1607.06673v1
+2016-09-19,Geometrical complexity of the antidots unit cell effect on the spin wave excitations spectra,"We have investigated theoretically (with micromagnetic simulations and plane
+wave method) and experimentally (with ferromagnetic resonance and Brillouin
+light scattering) three types of antidot lattices (ADLs) based on permalloy
+thin films with increased complexity of the unit cell: simple square,
+bi-component square and wave-like ADL. We have found that placing a small
+additional antidot in the center of the unit cell of the square ADL modify
+significantly the spin wave spectrum and its dependence on the orientation of
+the in-plane magnetic field. We also check the further changes of spin wave
+spectrum resulting from the introduction of air-gaps connecting small and large
+antidots. In particular, the presence of small antidots change the dependence
+of the frequency of the fundamental mode on the angle of the in-plane applied
+magnetic field. The air-gaps strongly discriminates the propagation of spin
+waves in two principal direction of ADL lattice, orthogonal to each other. In
+spite of these spectral changes, the spatial distribution of the spin wave
+amplitude generally preserves some similarities for all three structures. We
+also highlighted out the role of defects in the ADL in the observed spectra.
+The obtained results can be interesting for the magnonics applications of the
+magnonic crystals.",1609.05663v1
+2016-09-28,Quantitative separation of the anisotropic magnetothermopower and planar Nernst effect by the rotation of an in-plane thermal gradient,"A thermal gradient as the driving force for spin currents plays a key role in
+spin caloritronics. In this field the spin Seebeck effect (SSE) is of major
+interest and was investigated in terms of in-plane thermal gradients inducing
+perpendicular spin currents (transverse SSE) and out-of-plane thermal gradients
+generating parallel spin currents (longitudinal SSE). Up to now all spincaloric
+experiments employ a spatially fixed thermal gradient. Thus anisotropic
+measurements with respect to well defined crystallographic directions were not
+possible. Here we introduce a new experiment that allows not only the in-plane
+rotation of the external magnetic field, but also the rotation of an in-plane
+thermal gradient controlled by optical temperature detection. As a consequence,
+the anisotropic magnetothermopower and the planar Nernst effect in a permalloy
+thin film can be measured simultaneously and reveal a phase shift, that allows
+the quantitative separation of the thermopower, the anisotropic
+magnetothermopower and the planar Nernst effect.",1609.08822v1
+2017-12-20,Optical Manipulation of Magnetic Vortex Visualized in situ by 4D Electron Microscopy,"Understanding the fundamental dynamics of topological vortex and antivortex
+naturally formed in micro/nanoscale ferromagnetic building blocks under
+external perturbations is crucial to magnetic vortex based information
+processing and spintronic devices. All previous studies have focused on
+magnetic vortex-core switching via external magnetic fields, spin-polarized
+currents, or spin waves, which have largely prohibited the investigation of
+novel spin configurations that could emerge from the ground states in
+ferromagnetic disks and their underlying dynamics. Here, we report in situ
+visualization of femtosecond laser quenching induced magnetic vortex change in
+various symmetric ferromagnetic Permalloy disks by Lorentz phase imaging using
+4D electron microscopy. Besides the switching of magnetic vortex chirality and
+polarity, we observed with distinct occurrence frequencies a plenitude of
+complex magnetic structures that have never been observed by magnetic field or
+current assisted switching. These complex magnetic structures consist of a
+number of newly created topological magnetic defects (vortex and antivortex)
+strictly conserving the topological winding number, demonstrating the direct
+impact of topological invariant on the magnetization dynamics in ferromagnetic
+disks. Their spin configurations show mirror or rotation symmetry due to the
+geometrical confinement of the disks. Combined micromagnetic simulations with
+the experimental observations reveal the underlying magnetization dynamics and
+formation mechanism of the optical quenching induced complex magnetic
+structures. Their distinct occurrence rates are pertinent to their
+formation-growth energetics and pinning effects at the disk edge. Based on
+these findings, we propose a paradigm of optical-quenching-assisted fast
+switching of vortex cores for the control of magnetic vortex based information
+recording and spintronic devices.",1712.07280v1
+2017-12-20,Unifying ultrafast demagnetization and intrinsic Gilbert damping in Co/Ni bilayers with electronic relaxation near the Fermi surface,"The ability to controllably manipulate the laser-induced ultrafast magnetic
+dynamics is a prerequisite for future high speed spintronic devices. The
+optimization of devices requires the controllability of the ultrafast
+demagnetization time, , and intrinsic Gilbert damping, . In previous attempts
+to establish the relationship between and , the rare-earth doping of a
+permalloy film with two different demagnetization mechanism is not a suitable
+candidate. Here, we choose Co/Ni bilayers to investigate the relations between
+and by means of time-resolved magneto-optical Kerr effect (TRMOKE) via
+adjusting the thickness of the Ni layers, and obtain an approximately
+proportional relation between these two parameters. The remarkable agreement
+between TRMOKE experiment and the prediction of breathing Fermi-surface model
+confirms that a large Elliott-Yafet spin-mixing parameter is relevant to the
+strong spin-orbital coupling at the Co/Ni interface. More importantly, a
+proportional relation between and in such metallic films or heterostructures
+with electronic relaxation near Fermi surface suggests the local spin-flip
+scattering domains the mechanism of ultrafast demagnetization, otherwise the
+spin-current mechanism domains. It is an effective method to distinguish the
+dominant contributions to ultrafast magnetic quenching in metallic
+heterostructures by investigating both the ultrafast demagnetization time and
+Gilbert damping simultaneously. Our work can open a novel avenue to manipulate
+the magnitude and efficiency of Terahertz emission in metallic heterostructures
+such as the perpendicular magnetic anisotropic Ta/Pt/Co/Ni/Pt/Ta multilayers,
+and then it has an immediate implication of the design of high frequency
+spintronic devices.",1712.07323v1
+2018-01-16,Spin-orbit-torque and magnetic damping in tailored ferromagnetic bilayers,"We study spin-orbit-torque-driven ferromagnetic resonance (FMR) in
+ferromagnetic (FM) bilayers, consisting of Co and permalloy (Py), sandwiched
+between Pt and MgO layers. We find that the FM layer in contact with the Pt
+layers dominantly determines that spin Hall angle, which is consistent with the
+spin-transparency model. By contrast, the FMR linewidths are considerably
+influenced not only by the spin-pumping effect across the Pt|FM in terface but
+also by the spin relaxation such as two-magnon scattering at the FMMgO
+interface.The CoMgO interface leads to notably increased FMR linewidths, while
+the Py|MgO interface has less effect. This different contribution of each
+interface to the spin Hall angel and dissipation parameter suggests that the
+stack configuration of Pt|Co|Py|MgO requires less writing energy than
+Pt|Py|Co|MgO in spin-orbit-torque-driven magnetic switching. Our approach
+offers a promising method to optimize material parameters by engineering either
+interfaces in contact with the heavy-metal or the oxide layer.",1801.05131v2
+2018-05-31,Comparison of magnetic and structural properties of permalloy Ni80Fe20 grown by dc and high power impulse magnetron sputtering,"We study the microstructure and magnetic properties of Ni80Fe20 thin films
+grown by high power impulse magnetron sputtering (HiPIMS), and compare with
+films grown by dc magnetron sputtering (dcMS). The films were grown under a
+tilt angle of 35{\deg} to identical thickness of 37 nm using both techniques,
+at different pressure (0.13-0.73 Pa) and substrate temperature (room
+temperature and 100 {\deg}C). All of our films display effective in-plane
+uniaxial anisotropy with square easy axis and linear hard axis magnetization
+traces. X-ray diffraction reveals that there is very little change in grain
+size within the pressure and temperature ranges explored. However, variations
+in film density, obtained by X-ray reflectivity measurements, with pressure
+have a significant effect on magnetic properties such as anisotropy field (Hk)
+and coercivity (Hc). Depositions where adatom energy is high produce dense
+films, while low adatom energy results in void-rich films with higher Hk and
+Hc. The latter applies to our dcMS deposited films at room temperature and high
+pressure. However, the HiPIMS deposition method gives higher adatom energy than
+the dcMS and results in dense films with low Hk and Hc. The surface roughness
+is found to increase with increased pressure, in all cases, however it showed
+negligible contribution to the increase in Hk and Hc.",1805.12580v2
+2019-11-29,Real space observation of magnon interaction with driven space-time crystals,"The concept of Space-Time Crystals (STC), i.e. translational symmetry
+breaking in time and space, was recently proposed and experimentally
+demonstrated for quantum systems. Here, we transfer this concept to magnons and
+experimentally demonstrate a driven STC at room temperature. The STC is
+realized by strong homogeneous micro-wave pumping of a micron-sized permalloy
+(Py) stripe and is directly imaged by Scanning Transmission X-ray Microscopy
+(STXM). For a fundamental understanding of the formation of the STC,
+micromagnetic simulations are carefully adapted to model the experimental
+findings. Beyond the mere generation of a STC, we observe the formation of a
+magnonic band structure due to back folding of modes at the STC's Brillouin
+zone boundaries. We show interactions of magnons with the STC that appear as
+lattice scattering. This results in the generation of ultra short spin waves
+down to 100 nm wavelength that cannot be described by classical dispersion
+relations for linear spin wave excitations. We expect that room temperature
+STCs will be a useful tool to investigate non-linear wave physics, as they can
+be easily generated and manipulated to control their spatial and temporal band
+structure.",1911.13192v1
+2020-01-24,Dynamics of Spiral Spin Waves in Magnetic Nano-patches: Influence of Thickness and Shape,"We explore the dynamics of spiral spin waves in Permalloy nano-elements with
+variable aspect ratio of geometric dimensions, and their potential use as
+improved spin wave emitters with no or little biasing field required. Numerical
+results show that above a certain thickness, propagating spiral waves can be
+obtained in circular and square shaped elements in a flux closure state.
+VNA-FMR experiments on 20 nm (thin) and 80 nm (thick) samples confirm two type
+of spectra corresponding to different dispersions for thinner and thicker
+elements. We show that, for the thicker films, the vortex core region acts as a
+source of large amplitude spiral spin waves, which dominate over other modes.
+In case of the thinner elements, these modes are critically damped. For
+different shapes of the patch, we show that a rich collection of confined
+propagating modes can also be excited, modifying the final wave front and
+enriching the potential of the nano-dot as a spin wave emitter. We give an
+explanation for the intense spiral modes from the perspective of a balance of
+dipolar and exchange energies in the sample.",2001.09053v1
+2017-04-20,Coupled mode theory for the acoustic wave and spin wave interaction in the magphonic crystals: Propagating magnetoelastic waves,"We have investigated co-directional and contra-directional couplings between
+spin wave and acoustic wave in one-dimensional periodic structure (magphonic
+crystal). The system consists of two ferromagnetic layers alternating in space.
+We have taken into consideration materials commonly used in magnonics: yttrium
+iron garnet, CoFeB, permalloy, and cobalt. The coupled mode theory (CMT)
+formalism have been successfully implemented to describe magnetoelastic
+interaction as a periodic perturbation in the magphonic crystal. The results of
+CMT calculations have been verified by more rigorous simulations by
+frequency-domain plane wave method and time-domain finite element method. The
+presented resonant coupling in the magphonic crystal is an active in-space
+mechanism which spatially transfers energy between propagating spin and
+acoustic modes, thus creating propagating magnetoelastic wave. We have shown,
+that CMT analysis of the magnetoelastic coupling is an useful tool to optimize
+and design a spin wave - acoustic wave transducer based on a magphonic
+crystals. The effect of spin wave damping has been included to the model to
+discuss the efficiency of such a device. Our model shows that it is possible to
+obtain forward conversion of the acoustic wave to the spin wave in case of
+co-directional coupling and backward conversion in case of contra-directional
+coupling.",1704.06118v1
+2018-10-11,"Magnons in a Quasicrystal: Propagation, Localization and Extinction of Spin Waves in Fibonacci Structures","Magnonic quasicrystals exceed the possibilities of spin wave (SW)
+manipulation offered by regular magnonic crystals, because of their more
+complex SW spectra with fractal characteristics. Here, we report the direct
+x-ray microscopic observation of propagating SWs in a magnonic quasicrystal,
+consisting of dipolarly coupled permalloy nanowires arranged in a
+one-dimensional Fibonacci sequence. SWs from the first and second band as well
+as evanescent waves from the band gap between them are imaged. Moreover,
+additional mini-band gaps in the spectrum are demonstrated, directly indicating
+an influence of the quasiperiodicity of the system. The experimental results
+are interpreted using numerical calculations and we deduce a simple model to
+estimate the frequency position of the magnonic gaps in quasiperiodic
+structures. The demonstrated features of SW spectra in one-dimensional magnonic
+quasicrystals allows utilizing this class of metamaterials for magnonics and
+makes them an ideal basis for future applications.",1810.04931v2
+2019-01-03,Calculating spin transport properties from first principles: spin currents,"Local charge and spin currents are evaluated from the solutions of fully
+relativistic quantum mechanical scattering calculations for systems that
+include temperature-induced lattice and spin disorder as well as intrinsic
+alloy disorder. This makes it possible to determine material-specific spin
+transport parameters at finite temperatures. Illustrations are given for a
+number of important materials and parameters at 300 K. The spin-flip diffusion
+length $l_{\rm sf}$ of Pt is determined from the exponential decay of a spin
+current injected into a long length of thermally disordered Pt; we find $l_{\rm
+sf}^{\rm Pt}= 5.3\pm0.4 \,$nm. For the ferromagnetic substitutional disordered
+alloy Permalloy (Py), we inject currents that are fully polarized parallel and
+antiparallel to the magnetization and calculate $l_{\rm sf}$ from the
+exponential decay of their difference; we find $l_{\rm sf}^{\rm Py}= 2.8 \pm
+0.1 \,$nm. The transport polarization $\beta$ is found from the asymptotic
+polarization of a charge current in a long length of Py to be $\beta = 0.75 \pm
+0.01$. The spin Hall angle $\Theta_{\rm sH}$ is determined from the transverse
+spin current induced by the passage of a longitudinal charge current in
+thermally disordered Pt; our best estimate is $\Theta_{\rm sH}^{\rm Pt}=4.5 \pm
+1 \%$ corresponding to the experimental room temperature bulk resistivity $\rho
+=10.8 \mu \Omega \,$cm.",1901.00703v1
+2019-04-10,Optical excitation of propagating magnetostatic waves in an epitaxial Galfenol film by an ultrafast magnetic anisotropy change,"Using a time-resolved optically-pumped scanning optical microscopy technique
+we demonstrate the laser-driven excitation and propagation of spin waves in a
+20-nm film of a ferromagnetic metallic alloy Galfenol epitaxially grown on a
+GaAs substrate. In contrast to previous all-optical studies of spin waves we
+employ laser-induced thermal changes of magnetocrystalline anisotropy as an
+excitation mechanism. A tightly focused 70-fs laser pulse excites packets of
+magnetostatic surface waves with a $e^{-1}$ propagation length of 3.4 $\mu$m,
+which is comparable with that of permalloy. As a result, laser-driven
+magnetostatic spin waves are clearly detectable at distances up to 10 $\mu$m,
+which promotes epitaxial Galfenol films to the limited family of materials
+suitable for magnonic devices. A pronounced in-plane magnetocrystalline
+anisotropy of the Galfenol film offers an additional degree of freedom for
+manipulating the spin waves' parameters. Reorientation of an in-plane external
+magnetic field relative to the crystallographic axes of the sample tunes the
+frequency, amplitude and propagation length of the excited waves.",1904.05171v2
+2019-04-30,Tunable ferromagnetic resonance in coupled trilayers with crossed in-plane and perpendicular magnetic anisotropies,"A novel approach to tune the ferromagnetic resonance frequency of a soft
+magnetic Ni$_{80}$Fe$_{20}$ (Permalloy = Py) film with in-plane magnetic
+anisotropy (IMA) based on the controlled coupling to a hard magnetic
+NdCo$_\text{x}$ film with perpendicular magnetic anisotropy (PMA) through a
+non-magnetic Al spacer is studied. Using transverse magneto-optical Kerr effect
+(TMOKE), alternating gradient magnetometry (AGM) as well as vector network
+analyzer ferromagnetic resonance (VNA-FMR) spectroscopy, the influence of both
+Co concentration and Al spacer thickness on the static and dynamic magnetic
+properties of the coupled IMA/PMA system is investigated. Compared to a single
+Py film, two striking effects of the coupling between IMA and PMA layers can be
+observed in their FMR spectra. First, there is a significant increase in the
+zero-field resonance frequency from 1.3 GHz up to 6.6 GHz, and second, an
+additional frequency hysteresis occurs at low magnetic fields applied along the
+hard axis. The maximum frequency difference between the frequency branches for
+increasing and decreasing magnetic field is as high as 1 GHz, corresponding to
+a tunability of about 20% at external fields of typically less than $\pm$70 mT.
+The origin of the observed features in the FMR spectra is discussed by means of
+magnetization reversal curves.",1904.13275v1
+2018-02-18,Spin Solid versus Magnetic Charge Ordered State in Artificial Honeycomb Lattice of Connected Elements,"The nature of magnetic correlation at low temperature in two-dimensional
+artificial magnetic honeycomb lattice is a strongly debated issue. While
+theoretical researches suggest that the system will develop a novel zero
+entropy spin solid state as T --> 0 K, a confirmation to this effect in
+artificial honeycomb lattice of connected elements is lacking. We report on the
+investigation of magnetic correlation in newly designed artificial permalloy
+honeycomb lattice of ultra-small elements, with a typical length of ~ 12 nm,
+using neutron scattering measurements and temperature dependent micromagnetic
+simulations. Numerical modeling of the polarized neutron reflectometry data
+elucidates the temperature dependent evolution of spin correlation in this
+system. As temperature reduces to ~ 7 K, the system tends to develop novel spin
+solid state, manifested by the alternating distribution of magnetic vortex
+loops of opposite chiralities. Experimental results are complemented by
+temperature dependent micromagnetic simulations that confirm the dominance of
+spin solid state over local magnetic charge ordered state in the artificial
+honeycomb lattice with connected elements. Our results enable a direct
+investigation of novel spin solid correlation in the connected honeycomb
+geometry of two-dimensional artificial structure.",1802.06322v1
+2018-12-02,Direct detection of induced magnetic moment and efficient spin-to-charge conversion in graphene/ferromagnetic structures,"This article shows that the spin-to-charge current conversion in single-layer
+graphene (SLG) by means of the inverse Rashba-Edelstein effect (IREE) is made
+possible with the integration of this remarkable 2D-material with the unique
+ferrimagnetic insulator yttrium iron garnet (YIG = $Y_{3}Fe_{5}O_{12}$) as well
+as with the ferromagnetic metal permalloy (Py = $Ni_{81}Sb_{19}$). By means of
+X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD)
+techniques, we show that the carbon atoms of the SLG acquires an induced
+magnetic moment due to the proximity effect with the magnetic layer. The spin
+currents are generated in the magnetic layer by spin pumping from microwave
+driven ferromagnetic resonance and are detected by a dc voltage along the
+graphene layer, at room temperature. The spin-to-charge current conversion,
+occurring at the graphene layer, is explained by the extrinsic spin-orbit
+interaction (SOI) induced by the proximity effect with the ferromagnetic layer.
+The results obtained for the SLG/YIG and SLG/Py systems confirm very similar
+values for the IREE parameter, which are larger than the values reported in
+previous studies for SLG. We also report systematic investigations of the
+electronic and magnetic properties of the SLG/YIG by means of scanning
+tunneling microscopy (STM).",1812.00455v1
+2018-12-13,Scaling of intrinsic domain wall magneto-resistance with confinement in electromigrated nanocontacts,"In this work we study the evolution of intrinsic domain wall
+magnetoresistance (DWMR) with domain wall confinement. Clean permalloy notched
+half-ring nanocontacts are fabricated using a special ultra-high vacuum
+electromigration procedure to tailor the size of the wire in-situ and through
+the resulting domain wall confinement we tailor the domain wall width from a
+few tens of nm down to a few nm. Through measurements of the dependence of the
+resistance with respect to the applied field direction we extract the
+contribution of a single domain wall to the MR of the device, as a function of
+the domain wall width in the confining potential at the notch. In this size
+range, an intrinsic positive MR is found, which dominates over anisotropic MR,
+as confirmed by comparison to micromagnetic simulations. Moreover, the MR is
+found to scale monotonically with the size of the domain wall, $\delta_{DW}$,
+as 1/$\delta_{DW}^b$, with $b=2.31\pm 0.39 $. The experimental result is
+supported by quantum-mechanical transport simulations based on ab-initio
+density functional theory calculations.",1812.05689v1
+2020-08-29,Unveiling the polarity of the spin-to-charge current conversion in $Bi_2Se_3$,"We report an investigation of the spin- to charge-current conversion in
+sputter-deposited films of topological insulator $Bi_2Se_{3}$ onto single
+crystalline layers of YIG $(Y_{3}Fe_{5}O_{12})$ and polycrystalline films of
+Permalloy $(Py = Ni_{81}Fe_{19})$. Pure spin current was injected into the
+$Bi_{2}Se_{3}$ layer by means of the spin pumping process in which the spin
+precession is obtained by exciting the ferromagnetic resonance of the
+ferromagnetic film. The spin-current to charge-current conversion, occurring at
+the $Bi_{2}Se_{3}/$ferromagnet interface, was attribute to the inverse
+Rashba-Edelstein effect (IREE). By analyzing the data as a function of the
+$Bi_{2}Se_{3}$ thickness we calculated the IREE length used to characterize the
+efficiency of the conversion process and found that 1.2 pm
+$\leq|{\lambda}_{IREE}|\leq$ 2.2 pm. These results support the fact that the
+surface states of $Bi_{2}Se_{3}$ have a dominant role in the spin-charge
+conversion process, and the mechanism based on the spin diffusion process plays
+a secondary role. We also discovered that the spin- to charge-current mechanism
+in $Bi_{2}Se_{3}$ has the same polarity as the one in Ta, which is the opposite
+to the one in Pt. The combination of the magnetic properties of YIG and Py,
+with strong spin-orbit coupling and dissipationless surface states
+topologically protected of $Bi_{2}Se_{3}$ might lead to spintronic devices with
+fast and efficient spin-charge conversion.",2008.12900v1
+2021-02-28,Spin and charge interconversion in Dirac semimetal thin films,"We report spin-to-charge and charge-to-spin conversion at room temperature in
+heterostructure devices that interface an archetypal Dirac semimetal, Cd3As2,
+with a metallic ferromagnet, Ni0.80Fe0.20 (permalloy). The spin-charge
+interconversion is detected by both spin torque ferromagnetic resonance and
+ferromagnetic resonance driven spin pumping. Analysis of the symmetric and
+anti-symmetric components of the mixing voltage in spin torque ferromagnetic
+resonance and the frequency and power dependence of the spin pumping signal
+show that the behavior of these processes is consistent with previously
+reported spin-charge interconversion mechanisms in heavy metals, topological
+insulators, and Weyl semimetals. We find that the efficiency of spin-charge
+interconversion in Cd3As2/permalloy bilayers can be comparable to that in heavy
+metals. We discuss the underlying mechanisms by comparing our results with
+first principles calculations.",2103.00653v1
+2022-02-04,Three-axis torque investigation of interfacial exchange coupling in a NiFe/CoO bilayer micromagnetic disk,"Micrometer diameter bilayers of NiFe (permalloy, Py) and cobalt oxide (CoO)
+deposited on nanomechanical resonators were used to investigate exchange bias
+effects. The mechanical compliances of two resonator axes were enhanced by
+severing one torsion arm, resulting in a unique three-axis resonator that
+responds resonantly to torques generated by a three-axis RF field. Our
+technique permits simultaneous measurement of three orthogonal torque
+components. Measurements of the anisotropies associated with interfacial
+exchange coupling effects have been made. At cryogenic temperatures,
+observations of shifted linear hysteresis loops confirmed the presence of
+exchange bias from the Py/CoO interface. An in-plane rotating DC bias field was
+used to probe in-plane anisotropies through the out-of-plane torque. Training
+effects in the rotational hysteresis data were observed and showed that
+features due to interfacial coupling did not diminish irrespective of
+substantial training of the unidirectional anisotropy. The data from the
+rotational hysteresis loops were fit with parameters from a macrospin solution
+to the Landau-Lifshitz-Gilbert equation. Each parameter of the exchange bias
+model accounts for specific features of the rotational loop.",2202.02386v1
+2022-03-30,Tunable magnetically induced transparency spectra in magnon-magnon coupled Y3Fe5O12/permalloy bilayers,"Hybrid magnonic systems host a variety of characteristic quantum phenomena
+such as the magnetically-induced transparency (MIT) and Purcell effect, which
+are considered useful for future coherent quantum information processing. In
+this work, we experimentally demonstrate a tunable MIT effect in the
+Y3Fe5O12(YIG)/Permalloy(Py) magnon-magnon coupled system via changing the
+magnetic field orientations. By probing the magneto-optic effects of Py and
+YIG, we identify clear features of MIT spectra induced by the mode
+hybridization between the uniform mode of Py and the perpendicular standing
+spin-wave modes of YIG. By changing the external magnetic field orientations,
+we observe a tunable coupling strength between the YIG's spin-wave modes and
+the Py's uniform mode, upon the application of an out-of-plane magnetic field.
+This observation is theoretically interpreted by a geometrical consideration of
+the Py and YIG magnetization under the oblique magnetic field even at a
+constant interfacial exchange coupling. Our findings show high promise for
+investigating tunable coherent phenomena with hybrid magnonic platforms.",2203.16303v1
+2016-03-17,Proposal of a micromagnetic standard problem for ferromagnetic resonance simulations,"Nowadays, micromagnetic simulations are a common tool for studying a wide
+range of different magnetic phenomena, including the ferromagnetic resonance. A
+technique for evaluating reliability and validity of different micromagnetic
+simulation tools is the simulation of proposed standard problems. We propose a
+new standard problem by providing a detailed specification and analysis of a
+sufficiently simple problem. By analyzing the magnetization dynamics in a thin
+permalloy square sample, triggered by a well defined excitation, we obtain the
+ferromagnetic resonance spectrum and identify the resonance modes via Fourier
+transform. Simulations are performed using both finite difference and finite
+element numerical methods, with \textsf{OOMMF} and \textsf{Nmag} simulators,
+respectively. We report the effects of initial conditions and simulation
+parameters on the character of the observed resonance modes for this standard
+problem. We provide detailed instructions and code to assist in using the
+results for evaluation of new simulator tools, and to help with numerical
+calculation of ferromagnetic resonance spectra and modes in general.",1603.05419v1
+2017-01-09,Spin-Wave Modes in Transition from a Thin Film to a Full Magnonic Crystal,"Spin-wave modes are studied under the gradual transition from a flat thin
+film to a 'full' (one-dimensional) magnonic crystal. For this purpose, the
+surface of a pre-patterned 36.8 nm thin permalloy film was sequentially ion
+milled resulting in magnonic hybrid structures, referred to as
+surface-modulated magnonic crystals, with increasing modulation depth. After
+each etching step, ferromagnetic resonance measurements were performed yielding
+the spin-wave resonance modes in backward-volume and Damon-Eshbach geometry.
+The spin-wave spectra of these hybrid systems reveal an even larger variety of
+spin-wave states compared to the 'full' magnonic crystal. The measurements are
+corroborated by quasi-analytical theory and micromagnetic simulations in order
+to study the changing spin-wave mode character employing spin-wave mode
+profiles. In backward-volume geometry, a gradual transition from the uniform
+mode in the film limit to a fundamental mode in the thin part of the magnonic
+crystal was observed. Equivalently, the first and the second film modes are
+transform into a center and an edge mode of the thick part of the magnonic
+crystal. Simple transition rules from the $n^{\mathrm{th}}$ film mode to the
+$m^{\mathrm{th}}$ mode in the 'full' magnonic crystal are formulated unraveling
+the complex mode structure particularly in the backward-volume geometry. An
+analogous analysis was performed in the Damon-Eshbach geometry.",1702.05675v3
+2017-10-17,Dirac-Surface-State-Dominated Spin to Charge Current Conversion in the Topological Insulator $(Bi_{0.22}Sb_{0.78})_2Te_3$ Films at Room Temperature,"We report the spin to charge current conversation in an intrinsic topological
+insulator (TI) $(Bi_{0.22}Sb_{0.78})_2Te_3$ film at room temperature. The spin
+currents are generated in a thin layer of permalloy (Py) by two different
+processes, spin pumping (SPE) and spin Seebeck effects (SSE). In the first we
+use microwave-driven ferromagnetic resonance of the Py film to generate a SPE
+spin current that is injected into the TI $(Bi_{0.22}Sb_{0.78})_2Te_3$ layer in
+direct contact with Py. In the second we use the SSE in the longitudinal
+configuration in Py without contamination by the Nernst effect made possible
+with a thin NiO layer between the Py and $(Bi_{0.22}Sb_{0.78})_2Te_3$ layers.
+The spin-to-charge current conversion is attributed to the inverse Edelstein
+effect (IEE) made possible by the spin-momentum locking in the electron Fermi
+contours due to the Rashba field. The measurements by the two techniques yield
+very similar values for the IEE parameter, which are larger than the reported
+values in the previous studies on topological insulators.",1710.06224v1
+2019-03-13,"Epitaxial growth, structural characterization and exchange bias of non-collinear antiferromagnetic Mn$_{3}$Ir thin films","Antiferromagnetic materials are of great interest for spintronics. Here we
+present a comprehensive study of the growth, structural characterization, and
+resulting magnetic properties of thin films of the non-collinear
+antiferromagnet Mn$_{3}$Ir. Using epitaxial engineering on MgO (001) and
+Al$_{2}$O$_{3}$ (0001) single crystal substrates, we control the growth of
+cubic ${\gamma}$-Mn$_{3}$Ir in both (001) and (111) crystal orientations, and
+discuss the optimization of growth conditions to achieve high-quality crystal
+structures with low surface roughness. Exchange bias is studied in bilayers,
+with exchange bias fields as large as -29 mT (equivalent to a unidirectional
+anisotropy constant of 11.5 nJ cm$^{-2}$) measured in Mn$_{3}$Ir (111) /
+permalloy heterostructures at room temperature. In addition, a distinct
+dependence of blocking temperature on in-plane crystallographic direction in
+Mn$_{3}$Ir (001) / Py bilayers is observed. These findings are discussed in the
+context of chiral antiferromagnetic domain structures, and will inform progress
+towards topological antiferromagnetic spintronic devices.",1903.05539v1
+2019-05-16,Element-specific visualization of dynamic magnetic coupling in a Co/Py bilayer microstructure,"We present the element-specific and time resolved visualization of uniform
+ferromagnetic resonance excitations of a Permalloy (Py) disk - Cobalt (Co)
+stripe bilayer microstructure. The transverse high frequency component of the
+resonantly excited magnetization is sampled in the ps regime by a combination
+of ferromagnetic resonance (FMR) and scanning transmission X-ray microscopy
+(STXM- FMR) recording snapshots of the local magnetization precession of Py and
+Co with nanometer spatial resolution. The approach allows us to individually
+image the resonant dynamic response of each element, and we find that angular
+momentum is transferred from the Py disk to the Co stripe and vice versa at
+their respective resonances. The integral (cavity) FMR spectrum of our sample
+shows an unexpected additional third resonance. This resonance is observed in
+the STXM-FMR experiments as well and our microscopic findings suggest that it
+is governed by magnetic exchange between Py and Co, showing for the Co stripe a
+difference in relative phase of the magnetization due to stray field influence.",1905.06772v6
+2019-09-13,Monolayer MoS2 field effect transistor with low Schottky barrier height with ferromagnetic metal contacts,"Two-dimensional MoS2 has emerged as promising material for nanoelectronics
+and spintronics due to its exotic properties. However, high contact resistance
+at metal semiconductor MoS2 interface still remains an open issue. Here, we
+report electronic properties of field effect transistor devices using monolayer
+MoS2 channels and permalloy (Py) as ferromagnetic (FM) metal contacts.
+Monolayer MoS2 channels were directly grown on SiO2/Si substrate via chemical
+vapor deposition technique. The increase in current with back gate voltage
+shows the tunability of FET characteristics. The Schottky barrier height (SBH)
+estimated for Py/MoS2 contacts is found to be +28.8 meV (zero-bias), which is
+the smallest value reported so-far for any direct metal (magnetic or
+non-magnetic)/monolayer MoS2 contact. With the application of gate voltage (+10
+V), SBH shows a drastic reduction down to a value of -6.8 meV. The negative SBH
+reveals ohmic behavior of Py/MoS2 contacts. Low SBH with controlled ohmic
+nature of FM contacts is a primary requirement for MoS2 based spintronics and
+therefore using directly grown MoS2 channels in the present study can pave a
+path towards high performance devices for large scale applications.",1909.06014v1
+2020-02-19,Manipulation of coupling and magnon transport in magnetic metal-insulator hybrid structures,"Ferromagnetic metals and insulators are widely used for generation, control
+and detection of magnon spin signals. Most magnonic structures are based
+primarily on either magnetic insulators or ferromagnetic metals, while
+heterostructures integrating both of them are less explored. Here, by
+introducing a Pt/yttrium iron garnet (YIG)/permalloy (Py) hybrid structure
+grown on Si substrate, we studied the magnetic coupling and magnon transmission
+across the interface of the two magnetic layers. We found that within this
+structure, Py and YIG exhibit an antiferromagnetic coupling field as strong as
+150 mT, as evidenced by both the vibrating-sample magnetometry and polarized
+neutron reflectometry measurements. By controlling individual layer thicknesses
+and external fields, we realize parallel and antiparallel magnetization
+configurations, which are further utilized to control the magnon current
+transmission. We show that a magnon spin valve with an ON/OFF ratio of ~130%
+can be realized out of this multilayer structure at room temperature through
+both spin pumping and spin Seebeck effect experiments. Thanks to the efficient
+control of magnon current and the compatibility with Si technology, the
+Pt/YIG/Py hybrid structure could potentially find applications in magnon-based
+logic and memory devices.",2002.08266v1
+2020-02-20,Study of the spin-pump-induced inverse spin-Hall effect in Bi doped n-type Si,"An inverse spin Hall effect (ISHE) in n-type silicon was observed
+experimentally when conduction electrons were scattered on the spin-orbit
+potential of bismuth. The spin current in the silicon layer was generated by
+excitation of the magnetization precession during ferromagnetic resonance in a
+thin permalloy (Py) layer deposited on a Si layer doped by phosphor and
+bismuth. From the angular dependences of the dc voltage for different
+Py/n-Si:Bi structures aligned along the [011] or [100] crystal axes, we were
+able to distinguish the planar Hall effect (PHE) and ISHE contributions. The
+ISHE dc voltage signal was proportional to sin{\theta}*sin2{\theta} product for
+the structure aligned to the [011] crystal axis and to sin{\theta}*cos2{\theta}
+for the [100] direction. In addition, the PHE dc voltage was observed for the
+angles corresponded to the sin2{\theta} dependence. It means that for silicon
+as a many-valley semiconductor, the scattering of spins due to the spin-orbit
+potential induced by shallow donor in n-type material is dependent on the
+orientation of the valley axes relative to the direction of the magnetic field.",2002.08639v1
+2020-10-07,Correlation of uniaxial magnetic anisotropy axes and principal resistivities in polycrystalline ferromagnetic films,"In the present study, we demonstrate the measurement of resistivity tensor
+($\rho$) along the magnetic axes of a polycrystalline film of ferromagnetic
+permalloy (Py). To this end, conventional Hall-bar and a more recent extended
+van der Pauw methods were utilized for determining 2D $\rho$ in the film plane.
+The samples were prepared by normal incidence sputter deposition within an
+in-situ magnetic field to induce in-plane uniaxial magnetic anisotropy in the
+film. Since $\rho$ might be affected by the internal magnetization of the film,
+we performed measurements by rotation of a saturating magnetic field in the
+film plane. Both methods indicate that the average resistivity is lower along
+the easy axis of the film compared to the hard axis. Since X-ray diffraction
+results indicated no dominating texture in the film, we concluded that there is
+a correlation between uniaxial magnetic axes and principal resistivity axes.
+This is an important finding that allows determining the direction of magnetic
+anisotropy axes without magnetometry. The results also verify atomic or pair
+ordering to be the origin of uniaxial magnetic anisotropy in the Py since
+resistivity is sensitive to the level of order in solids. The extended van der
+Pauw utilized here can be easily performed on the as-received samples which is
+of practical interest.",2010.03554v3
+2020-10-15,Spin injection characteristics of Py/graphene/Pt by gigahertz and terahertz magnetization dynamics driven by femtosecond laser pulse,"Spin transport characteristics of graphene has been extensively studied so
+far. The spin transport along c-axis is however reported by rather limited
+number of papers. We have studied spin transport characteristics through
+graphene along c-axis with permalloy(Py)/graphene(Gr)/Pt by gigahertz (GHz) and
+terahertz (THz) magnetization dynamics driven by femtosecond laser pulses. The
+relatively simple sample structure does not require electrodes on the sample.
+The graphene layer was prepared by chemical vapor deposition and transferred on
+Pt film. The quality of graphene layer was characterized by Raman microscopy.
+Time resolved magneto-optical Kerr effect is used to characterize gigahertz
+magnetization dynamics. Magnetization precession is clearly observed both for
+Pt/Py and Pt/Gr/Py. The Gilbert damping constant of Pt/Py was 0.015, indicates
+spin pumping effect from Py to Pt. The Gilbert damping constant of Pt/Gr/Py is
+found to be 0.011, indicates spin injection is blocked by graphene layer. We
+have also performed the measurement of THz emission for Pt/Py and Pt/Gr/Py.
+While the THz emission is clearly observed for Pt/Py, a strong reduction of THz
+emission is observed for Pt/Gr/Py. With these two different experiments, and
+highly anisotropic resistivity of graphite, we conclude that the vertical spin
+transport is strongly suppressed by the graphene layer.",2010.07694v1
+2020-12-02,Engineered magnetization and exchange stiffness in direct-write Co-Fe nanoelements,"Media with engineered magnetization are essential building blocks in
+superconductivity, magnetism and magnon spintronics. However, the established
+thin-film and lithographic techniques insufficiently suit the realization of
+planar components with on-demand-tailored magnetization in the lateral
+dimension. Here, we demonstrate the engineering of the magnetic properties of
+CoFe-based nanodisks fabricated by the mask-less technique of focused electron
+beam induced deposition (FEBID). The material composition in the nanodisks is
+tuned \emph{in-situ} via the e-beam waiting time in the FEBID process and their
+post-growth irradiation with Ga ions. The magnetization $M_s$ and exchange
+stiffness $A$ of the disks are deduced from perpendicular ferromagnetic
+resonance measurements. The achieved $M_s$ variation in the broad range from
+$720$ emu/cm$^3$ to $1430$ emu/cm$^3$ continuously bridges the gap between the
+$M_s$ values of such widely used magnonic materials as permalloy and CoFeB. The
+presented approach paves a way towards nanoscale 2D and 3D systems with
+controllable and space-varied magnetic properties.",2012.01481v1
+2021-01-18,Systematic electrochemical etching of various metal tips for tunneling spectroscopy and scanning probe microscopy,"Hard point-contact spectroscopy and scanning probe microscopy/spectroscopy
+are powerful techniques for investigating materials with strong expandability.
+To support these studies, tips with various physical and chemical properties
+are required. To ensure the reproducibility of experimental results, the
+fabrication of tips should be standardized, and a controllable and convenient
+system should be set up. Here a systematic methodology to fabricate various
+tips is proposed, involving electrochemical etching reactions. The reaction
+parameters fall into four categories: solution, power supply, immersion depth,
+and interruption. An etching system was designed and built so that these
+parameters could be accurately controlled. With this system, etching parameters
+for copper, silver, gold, platinum/iridium alloy, tungsten, lead, niobium,
+iron, nickel, cobalt, and permalloy were explored and standardized. Among these
+tips, silver and niobium's new recipes were explored and standardized. Optical
+and scanning electron microscopies were performed to characterize the sharp
+needles. Relevant point-contact experiments were carried out with an etched
+silver tip to confirm the suitability of the fabricated tips.",2101.07090v1
+2021-05-03,Relaxation of a single defect spin by the low-frequency gyrotropic mode of a magnetic vortex,"We excite the gyrotropic mode of a magnetic vortex and observe the resulting
+effect on the spin state of a nearby nitrogen-vacancy (NV) defect in diamond.
+Thin permalloy disks fabricated on a diamond sample are magnetized in a vortex
+state in which the magnetization curls around a central core. The magnetization
+dynamics of this configuration are described by a discrete spectrum of confined
+magnon modes, as well as a low-frequency gyrotropic mode in which the vortex
+core precesses about its equilibrium position. Despite the spin transition
+frequencies being far-detuned from the modes of the ferromagnet, we observe
+enhanced relaxation of the NV spin when driving the gyrotropic mode. Moreover,
+we map the spatial dependence of the interaction between the vortex and the
+spin by translating the vortex core within the disk with an applied magnetic
+field, resulting in steplike motion as the vortex is pinned and de-pinned. The
+strong spin relaxation is observed when the vortex core is within approximately
+250 nm of the NV center defect. We attribute this effect to the higher
+frequencies in the spectrum of the magnetic fringe field arising from the
+soliton-like nature of the gyrotropic mode when driven with sufficiently large
+amplitude.",2105.00927v1
+2021-05-10,Observation of the Orbital Rashba-Edelstein Magnetoresistance,"We report the observation of magnetoresistance (MR) originating from the
+orbital angular momentum transport (OAM) in a Permalloy (Py) / oxidized Cu
+(Cu*) heterostructure: the orbital Rashba-Edelstein magnetoresistance. The
+angular dependence of the MR depends on the relative angle between the induced
+OAM and the magnetization in a similar fashion as the spin Hall
+magnetoresistance (SMR). Despite the absence of elements with large spin-orbit
+coupling, we find a sizable MR ratio, which is in contrast to the conventional
+SMR which requires heavy elements. By varying the thickness of the Cu* layer,
+we confirm that the interface is responsible for the MR, suggesting that the
+orbital Rashba-Edelstein effect is responsible for the generation of the OAM.
+Through Py thickness-dependence studies, we find that the effective values for
+the spin diffusion and spin dephasing lengths of Py are significantly larger
+than the values measured in Py / Pt bilayers, approximately by the factor of 2
+and 4, respectively. This implies that another mechanism beyond the
+conventional spin-based scenario is responsible for the MR observed in Py / Cu*
+structures originated in a sizeable transport of OAM. Our findings not only
+unambiguously demonstrate the current-induced torque without using any heavy
+element via the OAM channel but also provide an important clue towards the
+microscopic understanding of the role that OAM transport can play for
+magnetization dynamics.",2105.04495v2
+2021-06-18,The study of active geomagnetic shielding coils system for JUNO,"The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid
+scintillator (LS) detector for neutrino mass ordering and other neutrino
+physics research. The detector uses large-size $20$ inches photomultiplier
+tubes to detect photons from a liquid scintillator. The large PMTs are
+sensitive and easily affected such that the detection efficiency loses about
+60$\%$ under the geomagnetic field intensity ($\sim$500 mG). It has a
+significantly negative effect on the detector performance, and a compensation
+system is necessary for geomagnetic field shielding. As permalloys are easily
+rusted in water, a better way for the geomagnetic shielding is to apply an
+active compensation coils system. The simulations show that a set of 32
+circular coils can meet the experiment requirement. The residual magnetic field
+is less than 0.05 G in the Central Detector Photomultiplier Tube (CD-PMT)
+region (38.5-39.5 m in diameter). A prototype coil system with a 1.2 m was
+built to validate the simulation and the design. The measured data of prototype
+and simulation results are consistent with each other, and geomagnetic field
+intensity is effectively reduced by coils, verifying the shielding coils system
+design for JUNO. This study is expected to provide practical guidance for the
+PMT magnetic field shielding for future large-scale detector designs.",2106.09998v3
+2021-09-10,Anisotropic MagnetoMemristance,"In the last decade, nanoscale resistive devices with memory have been the
+subject of intense study because of their possible use in brain-inspired
+computing. However, operational endurance is one of the limiting factors in the
+adoption of such technology. For this reason, we discuss the emergence of
+current-induced memristance in magnetic materials, known for their durability.
+We show analytically and numerically that a single ferromagnetic layer can
+possess GHz memristance, due to a combination of two factors: a current-induced
+transfer of angular momentum (Zhang-Li torque) and the anisotropic
+magnetoresistance (AMR). We term the resulting effect the anisotropic
+magneto-memristance (AMM). We connect the AMM to the topology of the
+magnetization state, within a simple model of a 1-dimensional annulus-shaped
+magnetic layer, confirming the analytical results with micromagnetic
+simulations for permalloy. Our results open a new path towards the realization
+of single-layer magnetic memristive devices operating at GHz frequencies.",2109.05101v3
+2021-09-13,Effect of seed layer thickness on Ta crystalline phase and spin Hall angle,"Heavy metal-ferromagnet bilayer structures have attracted great research
+interest for charge-to-spin interconversion. In this work, we have investigated
+the effect of the permalloy seed layer on the Ta polycrystalline phase and its
+spin Hall angle. Interestingly, for the same deposition rates the crystalline
+phase of Ta deposited on Py seed layer strongly depends on the thickness of the
+seed layer. We have observed a phase transition from $\alpha$-Ta to
+($\alpha$+$\beta$)-Ta while increasing the Py seed layer thickness. The
+observed phase transition is attributed to the strain at interface between Py
+and Ta layers. Ferromagnetic resonance-based spin pumping studies reveal that
+the spin-mixing conductance in the to ($\alpha$+$\beta$)-Ta is relatively
+higher as compared to the to $\alpha$-Ta. Spin Hall angles of to $\alpha$-Ta
+and to ($\alpha$+$\beta$)-Ta are extracted from inverse spin Hall effect (ISHE)
+measurements. Spin Hall angle of the to ($\alpha$+$\beta$)-Ta is estimated to
+be $\theta$_SH=-0.15 which is relatively higher than that of to $\alpha$-Ta.
+Our systematic results connecting the phase of the Ta with seed layer and its
+effect on the efficiency of spin to charge conversion might resolve ambiguities
+across various literature and open up new functionalities based on the growth
+process for the emerging spintronic devices.",2109.06113v2
+2021-10-04,Separation of Artifacts from Spin-Torque Ferromagnetic Resonance Measurements of Spin-Orbit Torque for the Low-Symmetry van der Waals Semi-Metal ZrTe$_\textbf{3}$,"We measure spin-orbit torque generated by exfoliated layers of the
+low-symmetry semi-metal ZrTe$_3$ using the spin-torque ferromagnetic resonance
+(ST-FMR) technique. When the ZrTe$_3$ has a thickness greater than about 10 nm,
+artifacts due to spin pumping and/or resonant heating can cause the standard
+ST-FMR analysis to overestimate the true magnitude of the torque efficiency by
+as much as a factor of 30, and to indicate incorrectly that the spin-orbit
+torque depends strongly on the ZrTe$_3$ layer thickness. Artifact-free
+measurements can still be achieved over a substantial thickness range by the
+method developed recently to detect ST-FMR signals in the Hall geometry as well
+as the longitudinal geometry. ZrTe$_3$/Permalloy samples generate a
+conventional in-plane anti-damping spin torque efficiency
+$\xi_{||}^{\text{DL}}$ = 0.014 $\pm$ 0.004, and an unconventional in-plane
+field-like torque efficiency $|\xi_{||}^{\text{FL}}|$ = 0.003 $\pm$ 0.001. The
+out-of-plane anti-damping torque is negligible. We suggest that artifacts
+similarly interfere with the standard ST-FMR analysis for other van der Waals
+samples thicker than about 10 nm.",2110.01720v2
+2021-11-18,Spin transport at finite temperatures: A first-principles study for ferromagnetic$|$nonmagnetic interfaces,"Symmetry lowering at an interface leads to an enhancement of the effect of
+spin-orbit coupling and to a discontinuity of spin currents passing through the
+interface. This discontinuity is characterized by a ""spin-memory loss"" (SML)
+parameter $\delta$ that has only been determined directly at low temperatures.
+Although $\delta$ is believed to be significant in experiments involving
+interfaces between ferromagnetic and nonmagnetic metals, especially heavy
+metals like Pt, it is more often than not neglected to avoid introducing too
+many unknown interface parameters in addition to often poorly known bulk
+parameters like the spin-flip diffusion length $l_{\rm sf}$. In this work, we
+calculate $\delta$ along with the interface resistance $AR_{\rm I}$ and the
+spin-asymmetry parameter $\gamma$ as a function of temperature for Co$|$Pt and
+Py$|$Pt interfaces where Py is the ferromagnetic Ni$_{80}$Fe$_{20}$ alloy,
+permalloy. We use first-principles scattering theory to calculate the
+conductance as well as local charge and spin currents, modeling
+temperature-induced disorder with frozen thermal lattice and, for ferromagnetic
+materials, spin disorder within the adiabatic approximation. The bulk and
+interface parameters are extracted from the spin currents using a Valet-Fert
+model generalized to include SML.",2111.09731v1
+2022-01-14,Enhancement of supercurrent through ferromagnetic materials by interface engineering,"Josephson junctions containing ferromagnetic materials exhibit interesting
+physics and show promise as circuit elements for superconducting logic and
+memory. For memory applications, the properties of the junction should be
+controllable by changing the magnetic configuration inside the junction. To
+achieve good magnetic switching properties, one should choose a soft magnetic
+material such as NiFe (permalloy); however, NiFe exhibits poor supercurrent
+transmission in Josephson junctions. In this work we put thin layers of Ni on
+either side of the NiFe and characterize the magnetic behavior and supercurrent
+transmission properties of the Ni/NiFe/Ni trilayers as a function of Ni and
+NiFe thicknesses. Using a Ni thickness of 0.4 nm, we find that the magnetic
+switching behavior of the trilayers is not severely degraded relative to plain
+NiFe, while the maximum supercurrent in the $\pi$-state of the trilayer
+Josephson junctions is increased by a factor of four relative to that of NiFe
+junctions. We speculate that the supercurrent enhancement is due to the
+different spin-dependent transport properties of the Cu/Ni and Cu/NiFe
+interfaces.",2201.05444v4
+2022-07-06,Calculating the spin memory loss at Cu$|$metal interfaces from first principles,"The role played by interfaces in metallic multilayers is not only to change
+the momenta of incident electrons; their symmetry lowering also results in an
+enhancement of the effects of spin-orbit coupling, in particular the flipping
+of the spins of conduction electrons. This leads to a significant reduction of
+a spin current through a metallic interface that is quantitatively
+characterized by a dimensionless parameter $\delta$ called the spin memory loss
+(SML) parameter, the interface counterpart of the spin-flip diffusion length
+for bulk metals. In this paper we use first-principles scattering calculations
+that include temperature-induced lattice and spin disorder to systematically
+study three parameters that govern spin transport through metallic interfaces
+of Cu with Pt, Pd, Py (permalloy) and Co: the interface resistance, spin
+polarization and the SML. The value of $\delta$ for a Cu$|$Pt interface is
+found to be comparable to what we recently reported for a Au$|$Pt interface
+[Gupta {\it et al.}, Phys. Rev. Lett. 124, 087702 (2020)]. For Cu$|$Py and
+Cu$|$Co interfaces, $\delta$ decreases monotonically with increasing
+temperature to become negligibly small at room temperature. The calculated
+results are in good agreement with currently available experimental values in
+the literature. Inserting a Cu layer between Pt and the Py or Co layers
+slightly increases the total spin current dissipation at these ""compound""
+interfaces.",2207.02395v1
+2022-07-08,Measuring the magnon-photon coupling in shaped ferromagnets: tuning of the resonance frequency,"Cavity photons and ferromagnetic spins excitations can exchange information
+coherently in hybrid architectures, at speeds set by their mutual coupling
+strength. Speed enhancement is usually achieved by optimizing the geometry of
+the electromagnetic cavity. Here we show that the geometry of the ferromagnet
+plays also an important role, by setting the fundamental frequency of the
+magnonic resonator. Using focused ion beam patterning, we vary the aspect ratio
+of different Permalloy samples reaching operation frequencies above 10 GHz
+while working at low external magnetic fields. Additionally, we perform broad
+band ferromagnetic resonance measurements and cavity experiments that
+demonstrate that the magnon-photon coupling strength can be estimated using
+either open transmission lines or resonant cavities, yielding very good
+agreement. Finally, we describe a simple theoretical framework based on
+electromagnetic and micromagnetic simulations that successfully accounts for
+the experimental results. This approach can be used to design hybrid quantum
+systems exploiting whatsoever magnetostatic mode excited in ferromagnets of
+arbitrary size and shape and to tune their operation conditions.",2207.03829v3
+2022-08-09,Hybrid spin Hall nano-oscillators based on ferromagnetic metal/ferrimagnetic insulator heterostructures,"Spin-Hall nano-oscillators (SHNOs) are promising spintronic devices to
+realize current controlled GHz frequency signals in nanoscale devices for
+neuromorphic computing and creating Ising systems. However, traditional SHNOs
+-- devices based on transition metals -- have high auto-oscillation threshold
+currents as well as low quality factors and output powers. Here we demonstrate
+a new type of hybrid SHNO based on a permalloy (Py) ferromagnetic-metal
+nanowire and low-damping ferrimagnetic insulator, in the form of epitaxial
+lithium aluminum ferrite (LAFO) thin films. The superior characteristics of
+such SHNOs are associated with the excitation of larger spin-precession angles
+and volumes. We further find that the presence of the ferrimagnetic insulator
+enhances the auto-oscillation amplitude of spin-wave edge modes, consistent
+with our micromagnetic modeling. This hybrid SHNO expands spintronic
+applications, including providing new means of coupling multiple SHNOs for
+neuromorphic computing and advancing magnonics.",2208.04539v2
+2022-09-01,Large spin-to-charge conversion at the two-dimensional interface of transition metal dichalcogenides and permalloy,"Spin-to-charge conversion is an essential requirement for the implementation
+of spintronic devices. Recently, monolayers of semiconducting transition metal
+dichalcogenides (TMDs) have attracted considerable interest for spin-to-charge
+conversion due to their high spin-orbit coupling and lack of inversion symmetry
+in their crystal structure. However, reports of direct measurement of
+spin-to-charge conversion at TMD-based interfaces are very much limited. Here,
+we report on the room temperature observation of a large spin-to-charge
+conversion arising from the interface of Ni$_{80}$Fe$_{20}$ (Py) and four
+distinct large area ($\sim 5\times2$~mm$^2$) monolayer (ML) TMDs namely,
+MoS$_2$, MoSe$_2$, WS$_2$, and WSe$_2$. We show that both spin mixing
+conductance and the Rashba efficiency parameter ($\lambda_{IREE}$) scales with
+the spin-orbit coupling strength of the ML TMD layers. The $\lambda_{IREE}$
+parameter is found to range between $-0.54$ and $-0.76$ nm for the four
+monolayer TMDs, demonstrating a large spin-to-charge conversion. Our findings
+reveal that TMD/ferromagnet interface can be used for efficient generation and
+detection of spin current, opening new opportunities for novel spintronic
+devices.",2209.00332v1
+2022-09-08,Effects of the rf current and bias field direction on the transition from linear to non-linear gyrotropic dynamics in magnetic vortex structures,"We present a frequency-domain study of the dynamic behavior of a magnetic
+vortex core within a single Permalloy disk by means of electrical detection and
+micromagnetic simulations. When exciting the vortex core dynamics in a
+non-linear regime, the lineshape of the rectified dc signal reveals a resonance
+peak splitting which depends on the excitation amplitude. Using micromagnetic
+simulations, we show that at high excitation power the peak splitting
+originates from the nanosecond time scale quasi-periodic switching of the
+vortex core polarity. Using lock-in detection, the rectified voltage is
+integrated over a ms time scale, so that the net signal detected between the
+two resonant peaks for a given range of parameters cancels out. The results are
+in agreement with the reported effects of the in-plane static field magnitude
+on the gyration dynamics, and complement them by detailed analysis of the
+effects of the rf current amplitude and the azimuthal angle of the in-plane
+bias magnetic field. Systematic characterization shows that a transition from
+linear to nonlinear dynamical regime can be controlled by rf current as well as
+by varying the magnitude and the direction of the bias magnetic field.",2209.03701v2
+2022-09-27,Tailoring crosstalk between localized 1D spin-wave nanochannels using focused ion beams,"1D spin-wave conduits are envisioned as nanoscale components of
+magnonics-based logic and computing schemes for future generation electronics.
+`A-la-carte methods of versatile control of the local magnetization dynamics in
+such nanochannels are highly desired for efficient steering of the spin waves
+in magnonic devices. Here, we present a study of localized dynamical modes in
+1-$\mu$m-wide Permalloy conduits probed by microresonator ferromagnetic
+resonance technique. We clearly observe the lowest-energy edge mode in the
+microstrip after its edges were finely trimmed by means of focused Ne$^+$ ion
+irradiation. Furthermore, after milling the microstrip along its long axis by
+focused ion beams, creating consecutively $\sim$50 and $\sim$100 nm gaps,
+additional resonances emerge and are attributed to modes localized at the inner
+edges of the separated strips. To visualize the mode distribution, spatially
+resolved Brillouin light scattering microscopy was used showing an excellent
+agreement with the ferromagnetic resonance data and confirming the mode
+localization at the outer/inner edges of the strips depending on the magnitude
+of the applied magnetic field. Micromagnetic simulations confirm that the
+lowest-energy modes are localized within $\sim$15-nm-wide regions at the edges
+of the strips and their frequencies can be tuned in a wide range (up to 5 GHz)
+by changing the magnetostatic coupling (i.e. spatial separation) between the
+microstrips.",2209.13180v2
+2022-11-22,Generation of out-of-plane polarized spin current by spin swapping,"The generation of spin currents and their application to the manipulation of
+magnetic states is fundamental to spintronics. Of particular interest are
+chiral antiferromagnets that exhibit properties typical of ferromagnetic
+materials even though they have negligible magnetization. Here, we report the
+generation of a robust spin current with both in-plane and out-of-plane spin
+polarization in epitaxial thin films of the chiral antiferromagnet Mn3Sn in
+proximity to permalloy thin layers. By employing temperature-dependent
+spin-torque ferromagnetic resonance, we find that the chiral antiferromagnetic
+structure of Mn3Sn is responsible for an in-plane polarized spin current that
+is generated from the interior of the Mn3Sn layer and whose temperature
+dependence follows that of this layer's antiferromagnetic order. On the other
+hand, the out-of-plane spin polarized spin current is unrelated to the chiral
+antiferromagnetic structure and is instead the result of scattering from the
+Mn3Sn/permalloy interface. We substantiate the later conclusion by performing
+studies with several other non-magnetic metals all of which are found to
+exhibit out-of-plane polarized spin currents arising from the spin swapping
+effect.",2211.12398v1
+2023-01-30,Investigation of Ultrafast Demagnetization and Gilbert Damping and their Correlation in Different Ferromagnetic Thin Films Grown Under Identical Conditions,"Following the demonstration of laser-induced ultrafast demagnetization in
+ferromagnetic nickel, several theoretical and phenomenological propositions
+have sought to uncover its underlying physics. In this work we revisit the
+three temperature model (3TM) and the microscopic three temperature model
+(M3TM) to perform a comparative analysis of ultrafast demagnetization in
+20-nm-thick cobalt, nickel and permalloy thin films measured using an
+all-optical pump-probe technique. In addition to the ultrafast dynamics at the
+femtosecond timescales, the nanosecond magnetization precession and damping are
+recorded at various pump excitation fluences revealing a fluence-dependent
+enhancement in both the demagnetization times and the damping factors. We
+confirm that the Curie temperature to magnetic moment ratio of a given system
+acts as a figure of merit for the demagnetization time, while the
+demagnetization times and damping factors show an apparent sensitivity to the
+density of states at the Fermi level for a given system. Further, from
+numerical simulations of the ultrafast demagnetization based on both the 3TM
+and the M3TM, we extract the reservoir coupling parameters that best reproduce
+the experimental data and estimate the value of the spin flip scattering
+probability for each system. We discuss how the fluence-dependence of
+inter-reservoir coupling parameters so extracted may reflect a role played by
+nonthermal electrons in the magnetization dynamics at low laser fluences.",2301.12797v1
+2023-03-12,Unusual magnetic hysteresis and transition between vortex to double pole states arising from interlayer coupling in diamond shaped nanostructures,"Controlling the magnetic ground states at the nanoscale is a long-standing
+basic research problem and an important issue in magnetic storage technologies.
+Here, we designed a nanostructured material that exhibits very unusual
+hysteresis loops due to a transition between vortex and double pole states.
+Arrays of 700 nm diamond-shape nanodots consisting of Py(30 nm)/Ru(tRu)/Py(30
+nm) (Py, permalloy (Ni80Fe20)) trilayers were fabricated by interference
+lithography and e-beam evaporation. We show that varying the Ru interlayer
+spacer thickness (tRu) governs the interaction between the Py layers. We found
+this interaction mainly mediated by two mechanisms: magnetostatic interaction
+that favors antiparallel (antiferromagnetic, AFM) alignment of the Py layers
+and exchange interaction that oscillates between ferromagnetic (FM) and AFM
+couplings. For a certain range of Ru thicknesses, FM coupling dominates and
+forms magnetic vortices in the upper and lower Py layers. For Ru thicknesses at
+which AFM coupling dominates, the magnetic state in remanence is a double pole
+structure. Our results showed that the interlayer exchange coupling interaction
+remains finite even at 4 nm Ru thickness. The magnetic states in remanence,
+observed by Magnetic Force Microscopy (MFM), are in good agreement with
+corresponding hysteresis loops obtained by Magneto-Optic Kerr Effect (MOKE) and
+micromagnetic simulations.",2303.06735v1
+2023-03-20,Topological monopole's gauge field induced anomalous Hall effect in artificial honeycomb lattice,"Vortex magnetic structure in artificial honeycomb lattice provides a unique
+platform to explore emergent properties due to the additional Berry phase
+curvature imparted by chiral magnetization to circulating electrons via direct
+interaction. We argue that while the perpendicularly-aligned magnetic component
+leads to the quantized flux of monopole at the center of the Berry sphere, the
+in-plane vortex circulation of magnetization gives rise to unexpected
+non-trivial topological Berry phase due to the gauge field transformation. The
+unprecedented effect signifies the importance of vector potential in
+multiply-connected geometrical systems. Experimental confirmations to proposed
+hypotheses are obtained from Hall resistance measurements on permalloy
+honeycomb lattice. Investigation of the topological gauge transformation due to
+the in-plane chirality reveals anomalous quasi-oscillatory behavior in Hall
+resistance $R_{xy}$ as function of perpendicular field. The oscillatory nature
+of $R_{xy}$ is owed to the fluctuation in equilibrium current as a function of
+Fermi wave-vector $k_F$, envisaged under the proposed new formulation in this
+article. Our synergistic approach suggests that artificially tunable
+nanostructured material provides new vista to the exploration of topological
+phenomena of strong fundamental importance.",2303.11506v1
+2023-04-28,Persistent dynamic magnetic state in artificial honeycomb spin ice,"Topological magnetic charges, arising due to the non-vanishing magnetic flux
+on spin ice vertices, serve as the origin of magnetic monopoles that traverse
+the underlying lattice effortlessly. Unlike spin ice materials of atomic
+origin, the dynamic state in artificial honeycomb spin ice is conventionally
+described in terms of finite size domain wall kinetics that require magnetic
+field or current application. Contrary to this common understanding, here we
+show that thermally tunable artificial permalloy honeycomb lattice manifests a
+perpetual dynamic state due to self-propelled magnetic charge defect relaxation
+in the absence of any external tuning agent. Quantitative investigation of
+magnetic charge defect dynamics using neutron spin echo spectroscopy reveals
+sub-ns relaxation times that are comparable to monopole's relaxation in bulk
+spin ices. Most importantly, the kinetic process remains unabated at low
+temperature where thermal fluctuation is negligible. This suggests that dynamic
+phenomena in honeycomb spin ice are mediated by quasi-particle type entities,
+also confirmed by quantum Monte-Carlo simulations that replicate the kinetic
+behavior. Our research unveils a new `macroscopic' magnetic particle that
+shares many known traits of quantum particles, namely magnetic monopole and
+magnon.",2305.00093v1
+2023-08-23,Enhancing the Capture of Magnetic Nanoparticles Inside of Ferromagnetic Nanostructures Using External Magnetic Fields,"The influence of an external magnetic field upon the capture of 130 nm
+magnetic nanoparticles (MNPs) by ferromagnetic nanostructures was investigated.
+The magnetophoretic forces acting upon a nanoparticle were simulated in
+external magnetic fields parallel and perpendicular to ferromagnetic
+nanostructures consisting of arrays of antidots and dots. Changing the
+direction of the external field was found to dramatically alter the
+magnetophoretic forces acting on the particle and the trajectories of the MNPs.
+A field parallel to the nanostructures' surfaces generated magnetophoretic
+forces that directed the nanoparticle into the nanostructures. A perpendicular
+field produced forces directing particles onto the structures' surfaces.
+Nanostructures were etched into the surfaces of Permalloy films using ion beam
+lithography. MNPs were then deposited onto the films' surfaces under a parallel
+or perpendicular magnetic field. The distributions of particles in the
+nanostructures were analysed to obtain the capture efficiencies of each
+structure which indicate the proportion of particles trapped inside. Without an
+external field, the highest efficiency was displayed by arrays of circular
+antidots with circular dot arrays displaying the lowest. Antidot arrays
+displayed higher capture efficiencies than dot arrays. Addition of a field
+parallel to the surface significantly increased the capture efficiencies and
+addition of a field perpendicular to the surface decreased the efficiencies.
+Under the perpendicular field, the particles were instead caught on the outer
+edges of the nanostructures. These results suggest that application of a
+parallel external magnetic field promotes the capture of MNPs within
+ferromagnetic nanostructures and a perpendicular field increases the capture of
+MNPs onto the outer surface and edges of nanostructures.",2308.12321v1
+2023-08-28,External magnetic fields enhance capture of magnetic nanoparticles flowing through molded microfluidic channels by ferromagnetic nanostructures,"Magnetic nanoparticles (MNPs) have many applications which require MNPs to be
+captured and immobilized for their manipulation and sensing. For example, MNP
+sensors based on detecting changes to the ferromagnetic resonances of an
+antidot nanostructure exhibit better performance when the nanoparticles are
+captured within the antidot inclusions. This study investigates the influence
+of microfluidics upon the capture of MNPs by four geometries of antidot array
+nanostructures hollowed into 30 nm-thick Permalloy films. The nanostructures
+were exposed to a dispersion of 130 nm MNP clusters which passed through PDMS
+microfluidic channels with a 400 {\mu}m circular cross-section fabricated from
+wire molds. With the microfluidic flow of MNPs, the capture efficiency - the
+ratio between the number of nanoparticles captured inside of the antidot
+inclusions to the number outside the inclusions - decreased for all four
+geometries compared to previous results introducing the particles via droplets
+on the film surface. This indicates that most MNPs were passing over the
+nanostructures, since there were no significant magnetophoretic forces acting
+upon the particles. However, when a static magnetic field is applied, the
+magnetophoretic forces generated by the nanostructure are stronger and the
+capture efficiencies are significantly higher than those obtained using
+droplets. In particular, circular antidots demonstrated the highest capture
+efficiency among the four geometries of almost 83.1% when the magnetic field is
+parallel to the film plane. In a magnetic field perpendicular to the film, the
+circle antidots again show the highest capture efficiency of about 77%. These
+results suggest that the proportion of nanoparticles captured inside antidot
+inclusions is highest under a parallel magnetic field. Clearly, the geometry of
+the nanostructure has a strong influence on the capture of MNPs.",2308.14543v1
+2023-09-27,Correlation of Blocking and Néel Temperatures in Ultra-thin Metallic Antiferromagnets,"Nonvolatile spintronics-based devices that utilize electron spin both to
+store and transport information face a great challenge when scaled to nano
+dimensions due to loss of thermal stability and stray field induced disturbance
+in closely packed magnetic bits. The potential replacement of ferromagnetic
+materials with antiferromagnets may overcome some of these issues owing to the
+superior robustness of sublattice spin orientations to magnetic field
+disturbance as long as theyare kept well below the N\'eel temperature, which is
+hard to measure with conventional methods, especially in the ultrathin limit.
+In this work, we have employed spin pumping from a soft ferromagnetic NiFe
+layer into widely used ultrathin metallic antiferromagnet Ir20Mn80, FeMn, PtMn,
+PdMn or NiMn with thicknesses in the 0.7-3 nm range, as a probe to detect
+damping enhancement during magnetic phase transitions. Independent measurements
+of the blocking temperature with magnetometry reveal that temperature dependent
+shifts in the resonance peaks can also be used to measure the blocking
+temperature, allowing the analysis of the correlation between the N\'eel and
+blocking temperatures in trilayers with permalloy and antiferromagnetic layer
+separated by a 3 nm thick spacer layer. The thickness dependent
+characterization of thermal stability in antiferromagnets provides a key
+element for scalable and ultrafast antiferromagnetic spintronics.",2309.15545v1
+2023-10-17,Size-dependence and high temperature stability of radial vortex magnetic textures imprinted by superconductor stray fields,"Swirling spin textures, including topologically non-trivial states, such as
+skyrmions, chiral domain walls, and magnetic vortices, have garnered
+significant attention within the scientific community due to their appeal from
+both fundamental and applied points of view. However, their creation,
+controlled manipulation, and stability are typically constrained to certain
+systems with specific crystallographic symmetries, bulk, or interface
+interactions, and/or a precise stacking sequence of materials. Here, we make
+use of the stray field of YBa2Cu3O7-{\delta} superconducting microstructures in
+ferromagnet/superconductor hybrids to imprint magnetic radial vortices in
+permalloy at temperatures below the superconducting transition temperature
+(TC), a method easily extended to other ferromagnets with in-plane magnetic
+anisotropy. We examine the size dependence and temperature stability of the
+imprinted magnetic configurations. We show that above TC, magnetic domains
+retain memory of the imprinted spin texture. Micromagnetic modelling coupled
+with a SC field model reveals that the stabilization mechanism leading to this
+memory effect is mediated by microstructural defects. Superconducting control
+of swirling spin textures below and above the superconducting transition
+temperature holds promising prospects for shaping spintronics based on magnetic
+textures.",2310.11298v1
+2023-10-28,Einstein-de Haas torque as a discrete spectroscopic probe allows nanomechanical measurement of a magnetic resonance,"The Einstein-de Haas (EdH) effect is a fundamental, mechanical consequence of
+any temporal change of magnetism in an object. EdH torque results from
+conserving the object's total angular momentum: the angular momenta of all the
+specimen's magnetic moments, together with its mechanical angular momentum.
+Although the EdH effect is usually small and difficult to observe, it increases
+in magnitude with detection frequency. We explore the frequency-dependence of
+EdH torque for a thin film permalloy microstructure by employing a ladder of
+flexural beam modes (with five distinct resonance frequencies spanning from 3
+to 208 MHz) within a nanocavity optomechanical torque sensor via magnetic
+hysteresis curves measured at mechanical resonances. At low DC fields the
+gyrotropic resonance of a magnetic vortex spin texture overlaps the 208 MHz
+mechanical mode. The massive EdH mechanical torques arising from this
+co-resonance yield a fingerprint of vortex core pinning and depinning in the
+sample. The experimental results are discussed in relation to mechanical
+torques predicted from both macrospin (at high DC magnetic field) and
+finite-difference solutions to the Landau-Lifshitz-Gilbert (LLG) equation. A
+global fit of the LLG solutions to the frequency-dependent data reveals a
+statistically significant discrepancy between the experimentally observed and
+simulated torque phase behaviours at spin texture transitions that can be
+reduced through the addition of a time constant to the conversion between
+magnetic cross-product torque and mechanical torque, constrained by experiment
+to be in the range of 0.5 - 4 ns.",2310.18546v2
+2023-12-01,Nanocolumnar Material Platforms:Universal structural parameters revealed from optical anisotropy,"Nanostructures represent a frontier where meticulous attention to the control
+and assessment of structural dimensions becomes a linchpin for their seamless
+integration into diverse technological applications. By using integrative and
+comprehensive methodical series of studies, we investigate the evolution of the
+depolarization factors in the anisotropic Bruggeman effective medium
+approximation, that are extremely sensitive to the changes in critical
+dimensions of the nanostructure platforms. To this end, we fabricate spatially
+coherent highly-ordered slanted nanocolumns from zirconia, silicon, titanium,
+and permalloy on silicon substrates with varying column lengths using glancing
+angle deposition. In tandem, broad-spectral range Mueller matrix spectroscopic
+ellipsometry data, spanning from the near-infrared to the vacuum ultraviolet
+(0.72 eV to 6.5 eV), is analyzed with a best-match model approach based on the
+anisotropic Bruggeman effective medium theory. We thereby extracted the
+anisotropic optical properties including complex dielectric function,
+birefringence, and dichroism. Most notably, our research unveils a universal,
+material-independent inverse relationship between depolarization factors and
+column length. We envision that the presented universal relationship will
+permit accurate prediction of optical properties of nanocolumnar thin films
+improving their integration and optimization for optoelectronic and photonic
+device applications.",2312.00779v1
+2024-04-16,Reconfigurable spin-wave platform based on interplay between nanodots and waveguide in hybrid magnonic crystal,"We present a hybrid magnonic crystal composed of a chain of nanodots with
+strong perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interaction,
+positioned above a permalloy waveguide. The study examines two different
+magnetization states in the nanodots: a single-domain state and an egg-shaped
+skyrmion state. Due to the dipolar coupling between the dot and the waveguide,
+a strongly bound hybrid magnetization texture is formed in the system. Our
+numerical results show complex spin-wave spectra, combining the effects of
+periodicity, magnetization texture, and hybridization of the propagating waves
+in the waveguide with the dot/skyrmion modes. The systems are characterized by
+different band gap sizes. For the skyrmion state, the azimuthal modes confined
+to the skyrmion domain wall lead to the formation of flat bands at low
+frequencies, while at higher frequencies we identify among them modes
+interacting with the propagating waves, which can introduce additional
+non-Bragg band gaps, as well as isolated modes leading to the formation of
+bound states. On the other hand, the system with a single-domain state in
+nanodots offers a wide range of frequencies where the spin waves are
+predominantly in the waveguide. Thus, the study shows that the proposed hybrid
+magnonic crystals have many distinct functionalities, highlighting their
+reconfigurable potential, magnon-magnon couplings, mode localization, and bound
+states overlapping with the propagating waves. This opens up potential
+applications in analog and quantum magnonics, spin-wave filtering, and the
+establishment of magnonic neural networks.",2404.10493v1
+2002-07-26,Spin injection and spin accumulation in all-metal mesoscopic spin valves,"We study the electrical injection and detection of spin accumulation in
+lateral ferromagnetic metal-nonmagnetic metal-ferromagnetic metal (F/N/F) spin
+valve devices with transparent interfaces. Different ferromagnetic metals,
+permalloy (Py), cobalt (Co) and nickel (Ni), are used as electrical spin
+injectors and detectors. For the nonmagnetic metal both aluminium (Al) and
+copper (Cu) are used. Our multi-terminal geometry allows us to experimentally
+separate the spin valve effect from other magneto resistance signals such as
+the anomalous magneto resistance (AMR) and Hall effects. We find that the AMR
+contribution of the ferromagnetic contacts can dominate the amplitude of the
+spin valve effect, making it impossible to observe the spin valve effect in a
+'conventional' measurement geometry. In a 'non local' spin valve measurement we
+are able to completely isolate the spin valve signal and observe clear spin
+accumulation signals at T=4.2 K as well as at room temperature (RT). For
+aluminum we obtain spin relaxation lengths (lambda_{sf}) of 1.2 mu m and 600 nm
+at T=4.2 K and RT respectively, whereas for copper we obtain 1.0 mu m and 350
+nm. The spin relaxation times tau_{sf} in Al and Cu are compared with theory
+and results obtained from giant magneto resistance (GMR), conduction electron
+spin resonance (CESR), anti-weak localization and superconducting tunneling
+experiments. The spin valve signals generated by the Py electrodes (alpha_F
+lambda_F=0.5 [1.2] nm at RT [T=4.2 K]) are larger than the Co electrodes
+(alpha_F lambda_F=0.3 [0.7] nm at RT [T=4.2 K]), whereas for Ni (alpha_F
+lambda_F<0.3 nm at RT and T=4.2 K) no spin signal is observed. These values are
+compared to the results obtained from GMR experiments.",0207641v1
+2014-02-05,Spin Transfer Torque Generated by the Topological Insulator Bi_2Se_3,"Magnetic devices are a leading contender for implementing memory and logic
+technologies that are nonvolatile, that can scale to high density and high
+speed, and that do not suffer wear-out. However, widespread applications of
+magnetic memory and logic devices will require the development of efficient
+mechanisms for reorienting their magnetization using the least possible current
+and power. There has been considerable recent progress in this effort, in
+particular discoveries that spin-orbit interactions in heavy metal/ferromagnet
+bilayers can yield strong current-driven torques on the magnetic layer, via the
+spin Hall effect in the heavy metal or the Rashba-Edelstein effect in the
+ferromagnet. As part of the search for materials to provide even more efficient
+spin-orbit-induced torques, some proposals have suggested topological
+insulators (TIs), which possess a surface state in which the effects of
+spin-orbit coupling are maximal in the sense that an electron's spin
+orientation is locked relative to its propagation direction. Here we report
+experiments showing that charge current flowing in-plane in a thin film of the
+TI Bi_2Se_3 at room temperature can indeed apply a strong spin-transfer torque
+to an adjacent ferromagnetic permalloy (Py = Ni81Fe19) thin film, with a
+direction consistent with that expected from the topological surface state. We
+find that the strength of the torque per unit charge current density in the
+Bi_2Se_3 is greater than for any other spin-torque source material measured to
+date, even for non-ideal TI films wherein the surface states coexist with bulk
+conduction. Our data suggest that TIs have potential to enable very efficient
+electrical manipulation of magnetic materials at room temperature for memory
+and logic applications.",1402.1124v1
+2014-08-13,Sub-nanosecond signal propagation in anisotropy engineered nanomagnetic logic chains,"Energy efficient nanomagnetic logic (NML) computing architectures propagate
+and process binary information by relying on dipolar field coupling to reorient
+closely-spaced nanoscale magnets. Signal propagation in nanomagnet chains of
+various sizes, shapes, and magnetic orientations has been previously
+characterized by static magnetic imaging experiments with low-speed adiabatic
+operation; however the mechanisms which determine the final state and their
+reproducibility over millions of cycles in high-speed operation (sub-ns time
+scale) have yet to be experimentally investigated. Monitoring NML operation at
+its ultimate intrinsic speed reveals features undetectable by conventional
+static imaging including individual nanomagnetic switching events and
+systematic error nucleation during signal propagation. Here, we present a new
+study of NML operation in a high speed regime at fast repetition rates. We
+perform direct imaging of digital signal propagation in permalloy nanomagnet
+chains with varying degrees of shape-engineered biaxial anisotropy using
+full-field magnetic soft x-ray transmission microscopy after applying single
+nanosecond magnetic field pulses. Further, we use time-resolved magnetic
+photo-emission electron microscopy to evaluate the sub-nanosecond dipolar
+coupling signal propagation dynamics in optimized chains with 100 ps time
+resolution as they are cycled with nanosecond field pulses at a rate of 3 MHz.
+An intrinsic switching time of 100 ps per magnet is observed. These
+experiments, and accompanying macro-spin and micromagnetic simulations, reveal
+the underlying physics of NML architectures repetitively operated on nanosecond
+timescales and identify relevant engineering parameters to optimize performance
+and reliability.",1408.3157v1
+2015-12-25,Collective magnetic response of inhomogeneous nanoisland FeNi films around the percolation transition,"By using superconducting quantum interference device (SQUID) magnetometry we
+investigated anisotropic high-field (H < 7 T) low-temperature (10 K)
+magnetization response of inhomogeneous nanoisland FeNi films grown by rf
+sputtering deposition on Sitall (TiO2) glass substrates. In the grown FeNi
+films, the FeNi layer nominal thickness varied from 0.6 to 2.5 nm, across the
+percolation transition at the d_c=1.8 nm. We discovered that, beyond
+conventional spin-magnetism of Fe21Ni79 permalloy, the extracted out-of-plane
+magnetization response of the nanoisland FeNi films is not saturated in the
+range of investigated magnetic fields and exhibits paramagnetic-like behavior.
+We found that the anomalous out-of-plane magnetization response exhibits an
+escalating slope with increase in the nominal film thickness from 0.6 to 1.1
+nm, however, it decreases with further increase in the film thickness, and then
+practically vanishes on approaching the FeNi film percolation threshold. At the
+same time, the in-plane response demonstrates saturation behavior above 1.5-2
+T, competing with anomalously large diamagnetic-like response, which becomes
+pronounced at high magnetic fields. It is possible that the supported-metal
+interaction leads to the creation of a thin charge-transfer (CT) layer and a
+Schottky barrier at the FeNi film/Sitall (TiO2) interface. Then, in the system
+with nanoscale circular domains, the observed anomalous paramagnetic-like
+magnetization response can be associated with a large orbital moment of the
+localized electrons. The observed magnetization response is determined by the
+interplay between the paramagnetic- and diamagnetic-like contributions.",1512.07993v3
+2018-11-05,Reply to Comment on Optical detection of transverse spin-Seebeck effect in permalloy film using Sagnac interferometer microscopy (arXiv:1810.13220),"In their Comment, Kimling and Kuschel (hereafter the commenters) challenge
+our original interpretation of the magneto-optical Kerr effect (MOKE)
+measurements using ultrasensitive Sagnac interferometer, claiming that the
+transverse spin-Seebeck effect (TSSE) is not the only contribution to the
+measured change in the Kerr rotation angle from a Ni80Fe20 (NiFe) ferromagnetic
+(FM) slab subjected to a lateral temperature gradient in the presence of a
+magnetic field. The authors assert that: (1) the TSSE, in general, has not been
+completely proven so far, and that the existing theories, in particular the
+phonon magnon drag model that we have used in our publication, in fact cannot
+explain the original work of Uchida et al. (2) The commenters based their
+critique on an estimate of the magnitude of the measured effect, arguing that
+to observe the TSSE that we originally claimed, the temperature gradient in our
+measurements should have been much larger than the value we measured. In this
+Reply, firstly, we summarize previous literature reports on the TSSE response
+in FM metallic systems. Secondly, we dispute the estimate of the necessary
+large temperature gradient made by the commenters. Importantly, the Kerr effect
+sensitivity to spin accumulation (via the TSSE response) has not been
+recognized by the commenters, in fact it was mistakenly assumed that the Kerr
+effect sensitivity to the spin accumulation by the TSSE is the same as the Kerr
+sensitivity to the bulk magnetization change due to the temperature change. In
+conclusion, we show that the TSSE is the only viable interpretation of our
+original measurements, and that the phonon-magnon drag model is indeed capable
+of explaining our results.",1811.01877v1
+2014-06-01,Semi-Empirical Parameterization of Interatomic Interactions and Kinetics of the Atomic Ordering in Ni-Fe-C Permalloys and Elinvars,"Within the framework of the lattice-statics and static fluctuation-wave
+methods, the available energies of strain-induced interaction of
+interstitial-interstitial, interstitial-substitutional and
+substitutional-substitutional impurity atomic pairs are collected and analysed
+for f.c.c.-(Ni,Fe)-C solutions allowing for discrete atomic structure of the
+host-crystal lattice. The lattice spacings, elasticity moduli and/or
+quasi-elastic force parameters of the host-crystal lattice, and concentration
+coefficients of the dilatation of solid-solution lattice due to the respective
+solutes are selected as the input numerical experimental data used. The
+above-mentioned interaction energies prove to have non-monotonically decreasing
+and anisotropic dependences on discrete interatomic radius-vector, and
+themselves are strong and long-range. In all f.c.c.-(Ni,Fe)-base solutions,
+there is strain-induced attraction in many coordination shells. In general, the
+strain-induced interaction between impurity atoms in gamma-Fe is weaker than in
+alpha-Ni. The verification of applicability of the approximation of
+strain-induced interaction of impurities for f.c.c.-(Ni,Fe)-C alloys showed
+that it must be supplemented with additional short-range (electrochemical)
+repulsion in the first coordination shell. Nevertheless, in any case, the
+strain-induced interaction of impurity atoms must be taken into account for
+analysis of structure and properties of f.c.c.-(Ni,Fe)-base solutions. The
+Monte Carlo simulation procedures applied for constitution of a nanoscale
+Fe-C-austenite crystallite and based on analysis of the dependences of numbers
+of the different atomic configurations on C-C interatomic-interaction energies
+reveal correlation between the potential energy of such a modeling system and
+the numbers of iterations as well as Monte Carlo steps for the approach to
+constrained equilibrium.",1406.0164v1
+2021-03-24,Magnetism and Spin Dynamics in Room-Temperature van der Waals Magnet Fe$_5$GeTe$_2$,"Two-dimensional (2D) van der Waals (vdWs) materials have gathered a lot of
+attention recently. However, the majority of these materials have Curie
+temperatures that are well below room temperature, making it challenging to
+incorporate them into device applications. In this work, we synthesized a
+room-temperature vdW magnetic crystal Fe$_5$GeTe$_2$ with a Curie temperature
+T$_c = 332$ K, and studied its magnetic properties by vibrating sample
+magnetometry (VSM) and broadband ferromagnetic resonance (FMR) spectroscopy.
+The experiments were performed with external magnetic fields applied along the
+c-axis (H$\parallel$c) and the ab-plane (H$\parallel$ab), with temperatures
+ranging from 300 K to 10 K. We have found a sizable Land\'e g-factor difference
+between the H$\parallel$c and H$\parallel$ab cases. In both cases, the Land\'e
+g-factor values deviated from g = 2. This indicates contribution of orbital
+angular momentum to the magnetic moment. The FMR measurements reveal that
+Fe$_5$GeTe$_2$ has a damping constant comparable to Permalloy. With reducing
+temperature, the linewidth was broadened. Together with the VSM data, our
+measurements indicate that Fe$_5$GeTe$_2$ transitions from ferromagnetic to
+ferrimagnetic at lower temperatures. Our experiments highlight key information
+regarding the magnetic state and spin scattering processes in Fe$_5$GeTe$_2$,
+which promote the understanding of magnetism in Fe$_5$GeTe$_2$, leading to
+implementations of Fe$_5$GeTe$_2$ based room-temperature spintronic devices.",2103.13433v2
+2021-02-17,Growth optimization of TaN for superconducting spintronics,"We have optimized the growth of superconducting TaN thin films on \ch{SiO2}
+substrates via dc magnetron sputtering and extract a maximum superconducting
+transition temperature of $T_{\mathrm{c}}=5$ K as well as a maximum critical
+field $\mu_0H_{\mathrm{c2}}=(13.8\pm0.1)$ T. To investigate the impact of
+spin-orbit interaction in superconductor/ferromagnet heterostructures, we then
+analyze the magnetization dynamics of both normal state and superconducting
+TaN/\ch{Ni80Fe20}(Permalloy, Py)-bilayers as a function of temperature using
+broadband ferromagnetic resonance (bbFMR) spectroscopy. The phase sensitive
+detection of the microwave transmission signal is used to quantitatively
+extract the inverse current-induced torques of the bilayers. The results are
+compared to our previous study on NbN/Py-bilayers. In the normal state of TaN,
+we detect a positive damping-like current-induced torque $\sigma_{\mathrm{d}}$
+from the inverse spin Hall effect (iSHE) and a small field-like torque
+$\sigma_{\mathrm{f}}$ attributed to the inverse Rashba-Edelstein effect (iREE)
+at the TaN/Py-interface. In the superconducting state of TaN, we detect a
+negative $\sigma_{\mathrm{d}}$ attributed to the quasiparticle mediated inverse
+spin Hall effect (QMiSHE) and the unexpected manifestation of a large positive
+field-like $\sigma_{\mathrm{f}}$ of unknown origin matching our previous
+results for NbN/Py-bilayers.",2102.09018v1