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Physics and Astronomy › Atomic and Molecular Physics, and Optics

Magnetic properties of thin films

Works Count: 104921

Description

This cluster of papers focuses on the study and applications of magnetic skyrmions, spintronics, and related phenomena in ferromagnetic and antiferromagnetic materials. It covers topics such as room-temperature skyrmion lattice formation, spin-torque switching, magnetic domain-wall logic, magnon spintronics, and the use of nanoparticles in these systems.

Keywords

Skyrmions; Spintronics; Magnetic Tunnel Junctions; Spin Hall Effect; Room Temperature; Nanoparticles; Ferromagnetic Materials; Domain-Wall Logic; Magnonics; Antiferromagnetic Spintronics

Spin Current and Magnetoelectric Effect in Noncollinear Magnets

2005-07-28
Hosho Katsura , Naoto Nagaosa , Alexander V. Balatsky
A new mechanism of the magnetoelectric effect based on the spin supercurrent is theoretically presented in terms of a microscopic electronic model for noncollinear magnets. The electric polarization P(ij) produced … A new mechanism of the magnetoelectric effect based on the spin supercurrent is theoretically presented in terms of a microscopic electronic model for noncollinear magnets. The electric polarization P(ij) produced between the two magnetic moments S(i) and S(j) is given by P proportional e(ij) X (S(i) X S(j)) with e(ij) being the unit vector connecting the sites i and j. Applications to the spiral spin structure and the gauge theoretical interpretation are discussed.
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Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices

1988-11-21
M. N. Baibich , J.M. Broto , A. Fert +6 more
We have studied the magnetoresistance of (001)Fe/(001)Cr superlattices prepared by molecularbeam epitaxy. A huge magnetoresistance is found in superlattices with thin Cr layers: For example, with ${t}_{\mathrm{Cr}}=9$ \AA{}, at $T=4.2$ … We have studied the magnetoresistance of (001)Fe/(001)Cr superlattices prepared by molecularbeam epitaxy. A huge magnetoresistance is found in superlattices with thin Cr layers: For example, with ${t}_{\mathrm{Cr}}=9$ \AA{}, at $T=4.2$ K, the resistivity is lowered by almost a factor of 2 in a magnetic field of 2 T. We ascribe this giant magnetoresistance to spin-dependent transmission of the conduction electrons between Fe layers through Cr layers.
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Large Magnetoresistance at Room Temperature in Ferromagnetic Thin Film Tunnel Junctions

1995-04-17
Jagadeesh S. Moodera , Lisa R. Kinder , Terrilyn M. Wong +1 more
Ferromagnetic-insulator-ferromagnetic tunneling has been measured in CoFe $/$A${\mathrm{l}}_{2}$${\mathrm{O}}_{3}$ $/$Co or NiFe junctions. At 295, 77, and 4.2 K the fractional change in junction resistance with magnetic field, $\ensuremath{\Delta}R/R$, is 11.8%, … Ferromagnetic-insulator-ferromagnetic tunneling has been measured in CoFe $/$A${\mathrm{l}}_{2}$${\mathrm{O}}_{3}$ $/$Co or NiFe junctions. At 295, 77, and 4.2 K the fractional change in junction resistance with magnetic field, $\ensuremath{\Delta}R/R$, is 11.8%, 20%, and 24%, respectively. The value at 4.2 K is consistent with Julliere's model based on the spin polarization of the conduction electrons of the magnetic films. $\ensuremath{\Delta}R/R$ changes little with a small voltage bias, whereas it decreases significantly at higher bias $(>0.1\mathrm{V})$, in qualitative agreement with Slonczewski's model. These junctions have potential use as low-power field sensors and memory elements.

Skyrmion Lattice in a Chiral Magnet

2009-02-13
S. Mühlbauer , B. Binz , Florian Jonietz +5 more
Skyrmions represent topologically stable field configurations with particle-like properties. We used neutron scattering to observe the spontaneous formation of a two-dimensional lattice of skyrmion lines, a type of magnetic vortex, … Skyrmions represent topologically stable field configurations with particle-like properties. We used neutron scattering to observe the spontaneous formation of a two-dimensional lattice of skyrmion lines, a type of magnetic vortex, in the chiral itinerant-electron magnet MnSi. The skyrmion lattice stabilizes at the border between paramagnetism and long-range helimagnetic order perpendicular to a small applied magnetic field regardless of the direction of the magnetic field relative to the atomic lattice. Our study experimentally establishes magnetic materials lacking inversion symmetry as an arena for new forms of crystalline order composed of topologically stable spin states.
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Magnetic Domain-Wall Racetrack Memory

2008-04-10
S. Parkin , Masamitsu Hayashi , Luc Thomas
Recent developments in the controlled movement of domain walls in magnetic nanowires by short pulses of spin-polarized current give promise of a nonvolatile memory device with the high performance and … Recent developments in the controlled movement of domain walls in magnetic nanowires by short pulses of spin-polarized current give promise of a nonvolatile memory device with the high performance and reliability of conventional solid-state memory but at the low cost of conventional magnetic disk drive storage. The racetrack memory described in this review comprises an array of magnetic nanowires arranged horizontally or vertically on a silicon chip. Individual spintronic reading and writing nanodevices are used to modify or read a train of approximately 10 to 100 domain walls, which store a series of data bits in each nanowire. This racetrack memory is an example of the move toward innately three-dimensional microelectronic devices.

Topological properties and dynamics of magnetic skyrmions

2013-12-01
Naoto Nagaosa , Yoshinori Tokura

Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions

2004-10-31
Shinji Yuasa , Taro Nagahama , Akio Fukushima +2 more

Monodisperse FePt Nanoparticles and Ferromagnetic FePt Nanocrystal Superlattices

2000-03-17
Shouheng Sun , C. B. Murray , D. Weller +2 more
Synthesis of monodisperse iron-platinum (FePt) nanoparticles by reduction of platinum acetylacetonate and decomposition of iron pentacarbonyl in the presence of oleic acid and oleyl amine stabilizers is reported. The FePt … Synthesis of monodisperse iron-platinum (FePt) nanoparticles by reduction of platinum acetylacetonate and decomposition of iron pentacarbonyl in the presence of oleic acid and oleyl amine stabilizers is reported. The FePt particle composition is readily controlled, and the size is tunable from 3- to 10-nanometer diameter with a standard deviation of less than 5%. These nanoparticles self-assemble into three-dimensional superlattices. Thermal annealing converts the internal particle structure from a chemically disordered face-centered cubic phase to the chemically ordered face-centered tetragonal phase and transforms the nanoparticle superlattices into ferromagnetic nanocrystal assemblies. These assemblies are chemically and mechanically robust and can support high-density magnetization reversal transitions.

Giant magnetoresistance in heterogeneous Cu-Co alloys

1992-06-22
A. E. Berkowitz , J. R. Mitchell , M. J. Carey +6 more
We have observed giant magnetoresistance in heterogeneous thin film Cu-Co alloys consisting of ultrafine Co-rich precipitate particles in a Cu-rich matrix. The magnetoresistance scales inversely with the average particle diameter. … We have observed giant magnetoresistance in heterogeneous thin film Cu-Co alloys consisting of ultrafine Co-rich precipitate particles in a Cu-rich matrix. The magnetoresistance scales inversely with the average particle diameter. This behavior is modeled by including spin-dependent scattering at the interfaces between the particles and the matrix, as well as the spin-dependent scattering in the Co-rich particles.

Spin-dependent tunneling conductance of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Fe</mml:mi><mml:mi>|</mml:mi><mml:mi mathvariant="normal">MgO</mml:mi><mml:mi>|</mml:mi><mml:mi mathvariant="normal">Fe</mml:mi></mml:math>sandwiches

2001-01-08
W. H. Butler , X.-G. Zhang , T. C. Schulthess +1 more
We present first-principles based calculations of the tunneling conductance and magnetoconductance of epitaxial $\mathrm{Fe}(100)|\mathrm{MgO}(100)|\mathrm{Fe}(100)$ sandwiches. Our results indicate that tunneling is much more interesting and complicated than the simple barrier … We present first-principles based calculations of the tunneling conductance and magnetoconductance of epitaxial $\mathrm{Fe}(100)|\mathrm{MgO}(100)|\mathrm{Fe}(100)$ sandwiches. Our results indicate that tunneling is much more interesting and complicated than the simple barrier model used previously. We obtain the following general results: (1) Tunneling conductance depends strongly on the symmetry of the Bloch states in the electrodes and of the evanescent states in the barrier layer. (2) Bloch states of different symmetry decay at different rates within the barrier. The decay rate is determined by the complex energy bands of the same symmetry in the barrier. (3) There may be quantum interference between the decaying states in the barrier. This leads to an oscillatory dependence of the tunneling current on ${k}_{\ensuremath{\Vert}}$ and a damped oscillatory dependence on barrier thickness. (4) Interfacial resonance states can allow particular Bloch states to tunnel efficiently through the barrier. For $\mathrm{Fe}(100)|\mathrm{MgO}(100)|\mathrm{Fe}(100)$ our calculations indicate that quite different tunneling mechanisms dominate the conductance in the two spin channels. In the majority channel the conductance is primarily via Bloch electrons with small transverse momentum. One particular state with ${\ensuremath{\Delta}}_{1}$ symmetry is able to effectively couple from the Fe into the MgO. In the minority channel the conductance is primarily through interface resonance states especially for thinner layers. We predict a large magnetoresistance that increases with barrier thickness.
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New Magnetic Anisotropy

1957-02-01
W. H. Meiklejohn , C. P. Bean
A new type of magnetic anisotropy has been discovered which is best described as an exchange anisotropy. This anisotropy is the result of an interaction between an antiferromagnetic material and … A new type of magnetic anisotropy has been discovered which is best described as an exchange anisotropy. This anisotropy is the result of an interaction between an antiferromagnetic material and a ferromagnetic material. The material that exhibits this exchange anisotropy is a compact of fine particles of cobalt with a cobaltous oxide shell. The effect occurs only below the N\'eel temperature of the antiferromagnetic material, which is essentially room temperature for the cobaltous oxide. An exchange torque is inferred to exist between the metal and oxide which has a maximum value at 77\ifmmode^\circ\else\textdegree\fi{}K of \ensuremath{\sim}2 dyne-cm/${\mathrm{cm}}^{2}$ of interface.

Spin-Torque Switching with the Giant Spin Hall Effect of Tantalum

2012-05-03
Luqiao Liu , Chi‐Feng Pai , Yi Li +3 more
We report a giant spin Hall effect (SHE) in {\beta}-Ta that generates spin currents intense enough to induce efficient spin-transfer-torque switching of ferromagnets, thereby providing a new approach for controlling … We report a giant spin Hall effect (SHE) in {\beta}-Ta that generates spin currents intense enough to induce efficient spin-transfer-torque switching of ferromagnets, thereby providing a new approach for controlling magnetic devices that can be superior to existing technologies. We quantify this SHE by three independent methods and demonstrate spin-torque (ST) switching of both out-of-plane and in-plane magnetized layers. We implement a three-terminal device that utilizes current passing through a low impedance Ta-ferromagnet bilayer to effect switching of a nanomagnet, with a higher-impedance magnetic tunnel junction for read-out. The efficiency and reliability of this device, together with its simplicity of fabrication, suggest that this three-terminal SHE-ST design can eliminate the main obstacles currently impeding the development of magnetic memory and non-volatile spin logic technologies.
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Emission of spin waves by a magnetic multilayer traversed by a current

1996-10-01
L. Berger
The interaction between spin waves and itinerant electrons is considerably enhanced in the vicinity of an interface between normal and ferromagnetic layers in metallic thin films. This leads to a … The interaction between spin waves and itinerant electrons is considerably enhanced in the vicinity of an interface between normal and ferromagnetic layers in metallic thin films. This leads to a local increase of the Gilbert damping parameter which characterizes spin dynamics. When a dc current crosses this interface, stimulated emission of spin waves is predicted to take place. Beyond a certain critical current density, the spin damping becomes negative; a spontaneous precession of the magnetization is predicted to arise. This is the magnetic analog of the injection laser. An extra dc voltage appears across the interface, given by an expression similar to that for the Josephson voltage across a superconducting junction. \textcopyright{} 1996 The American Physical Society.

Local spin density functional approach to the theory of exchange interactions in ferromagnetic metals and alloys

1987-05-01
A. I. Liechtenstein , M. I. Katsnelson , V. P. Antropov +1 more

Layered Magnetic Structures: Evidence for Antiferromagnetic Coupling of Fe Layers across Cr Interlayers

1986-11-10
P. Grünberg , R. Schreiber , Y. Pang +2 more
We investigated exchange coupling of Fe layers across Au and Cr interlayers by means of light scattering from spin waves. For Au interlayers we find a continuous decrease of this … We investigated exchange coupling of Fe layers across Au and Cr interlayers by means of light scattering from spin waves. For Au interlayers we find a continuous decrease of this coupling to zero as the Au thickness is increased from 0 to \ensuremath{\cong}20 \AA{}. For Cr interlayers of proper thickness we find antiferromagnetic coupling of the Fe layers. In small external fields such double layers order antiparallel with their magnetization perpendicular to the external field, in analogy to the spin-flop phase of antiferromagnets.
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The emergence of spin electronics in data storage

2007-11-01
Claude Chappert , A. Fert , F. Nguyen Van Dau

Magnetic Properties of Cu-Mn Alloys

1957-06-01
Kei Yosida
The polarization of conduction electrons due to $s\ensuremath{-}d$ interaction in CuMn alloys is investigated. The uniform polarization due to the first order perturbed energy corresponding to the Fr\"ohlich-Nabarro and Zener … The polarization of conduction electrons due to $s\ensuremath{-}d$ interaction in CuMn alloys is investigated. The uniform polarization due to the first order perturbed energy corresponding to the Fr\"ohlich-Nabarro and Zener mechanism is shown to be completely modified by the first order perturbation of the wave functions and the polarization is concentrated in the neighborhood of the Mn ions. At the same time it is shown that the Fr\"ohlich-Nabarro interaction is included in the Ruderman-Kittel result as one component. The electronic $g$-value of Mn ions and the Knight shift of the Cu-nuclei are also discussed from this point of view.

Giant magnetoresistive in soft ferromagnetic multilayers

1991-01-01
B. Diény , V. S. Speriosu , S. Parkin +3 more
We show that the in-plane magnetoresistance of sandwiches of uncoupled ferromagnetic (${\mathrm{Ni}}_{81}$${\mathrm{Fe}}_{19}$,${\mathrm{Ni}}_{80}$${\mathrm{Co}}_{20}$,Ni) layers separated by ultrathin nonmagnetic metallic (Cu,Ag,Au) layers is strongly increased when the magnetizations of the two ferromagnetic … We show that the in-plane magnetoresistance of sandwiches of uncoupled ferromagnetic (${\mathrm{Ni}}_{81}$${\mathrm{Fe}}_{19}$,${\mathrm{Ni}}_{80}$${\mathrm{Co}}_{20}$,Ni) layers separated by ultrathin nonmagnetic metallic (Cu,Ag,Au) layers is strongly increased when the magnetizations of the two ferromagnetic layers are aligned antiparallel. Using NiFe layers, we report a relative change of resistance of 5.0% in 10 Oe at room temperature. The comparison between different ferromagnetic materials (alloys or pure elements) leads us to emphasize the role of bulk rather than interfacial spin-dependent scattering in these structures, in contrast to Fe/Cr multilayers.

Skyrmions on the track

2013-03-01
A. Fert , Vincent Cros , J. Sampaio

Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers

2004-10-31
S. Parkin , Christian Kaiser , Alex Panchula +4 more

Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange

1989-03-01
G. Binasch , P. Grünberg , F. Saurenbach +1 more
The electrical resistivity of Fe-Cr-Fe layers with antiferromagnetic interlayer exchange increases when the magnetizations of the Fe layers are aligned antiparallel. The effect is much stronger than the usual anisotropic … The electrical resistivity of Fe-Cr-Fe layers with antiferromagnetic interlayer exchange increases when the magnetizations of the Fe layers are aligned antiparallel. The effect is much stronger than the usual anisotropic magnetoresistance and further increases in structures with more than two Fe layers. It can be explained in terms of spin-flip scattering of conduction electrons caused by the antiparallel alignment of the magnetization.

Current-Driven Magnetization Reversal and Spin-Wave Excitations in Co<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>/</mml:mi></mml:math>Cu<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>/</mml:mi></mml:math>Co Pillars

2000-04-03
J. A. Katine , F. J. Albert , R. A. Buhrman +2 more
Using thin film pillars approximately 100 nm in diameter, containing two Co layers of different thicknesses separated by a Cu spacer, we examine the process by which the scattering from … Using thin film pillars approximately 100 nm in diameter, containing two Co layers of different thicknesses separated by a Cu spacer, we examine the process by which the scattering from the ferromagnetic layers of spin-polarized currents flowing perpendicular to the layers causes controlled reversal of the moment direction in the thin Co layer. The well-defined geometry permits a quantitative analysis of this spin-transfer effect, allowing tests of competing theories for the mechanism and also new insight concerning magnetic damping. When large magnetic fields are applied, the spin-polarized current no longer fully reverses the magnetic moment, but instead stimulates spin-wave excitations.
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Giant magnetic tunneling effect in Fe/Al2O3/Fe junction

1995-01-01
T. Miyazaki , N. Tezuka

Current-driven dynamics of chiral ferromagnetic domain walls

2013-06-14
Satoru Emori , Uwe Bauer , Sung–Min Ahn +2 more
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Effect of Correlation on the Ferromagnetism of Transition Metals

1963-03-01
Martin C. Gutzwiller
Received 27 September 1962DOI:https://doi.org/10.1103/PhysRevLett.10.159©1963 American Physical Society Received 27 September 1962DOI:https://doi.org/10.1103/PhysRevLett.10.159©1963 American Physical Society

Conductance and exchange coupling of two ferromagnets separated by a tunneling barrier

1989-04-01
J. C. Slonczewski
A theory is given for three closely related effects involving a nonmagnetic electron-tunneling barrier separating two ferromagnetic conductors. The first is Julliere's magnetic valve effect, in which the tunnel conductance … A theory is given for three closely related effects involving a nonmagnetic electron-tunneling barrier separating two ferromagnetic conductors. The first is Julliere's magnetic valve effect, in which the tunnel conductance depends on the angle \ensuremath{\theta} between the moments of the two ferromagnets. One finds that discontinuous change of the potential at the electrode-barrier interface diminishes the spin-polarization factor governing this effect and is capable of changing its sign. The second is an effective interfacial exchange coupling -J cos\ensuremath{\theta} between the ferromagnets. One finds that the magnitude and sign of J depend on the height of the barrier and the Stoner splitting in the ferromagnets. The third is a new, irreversible exchange term in the coupled dynamics of the ferromagnets. For one sign of external voltage V, this term describes relaxation of the Landau-Lifshitz type. For the opposite sign of V, it describes a pumping action which can cause spontaneous growth of magnetic oscillations. All of these effects were investigated consistently by analyzing the transmission of charge and spin currents flowing through a rectangular barrier separating free-electron metals. In application to Fe-C-Fe junctions, the theory predicts that the valve effect is weak and that the coupling is antiferromagnetic (J&lt;0). Relations connecting the three effects suggest experiments involving small spatial dimensions.

Giant magnetoresistance in nonmultilayer magnetic systems

1992-06-22
John Q. Xiao , J. S. Jiang , C. L. Chien
We have observed isotropic giant magnetoresistance (GMR) in nonmultilayer magnetic systems using granular magnetic solids. We show that GMR occurs in magnetically inhomogeneous media containing nonaligned ferromagnetic entities on a … We have observed isotropic giant magnetoresistance (GMR) in nonmultilayer magnetic systems using granular magnetic solids. We show that GMR occurs in magnetically inhomogeneous media containing nonaligned ferromagnetic entities on a microscopic scale. The GMR is determined by the orientations of the magnetization axes, the density, and the size of the ferromagnetic entities.

Microwave oscillations of a nanomagnet driven by a spin-polarized current

2003-09-01
S. I. Kiselev , Jack Sankey , I. N. Krivorotov +4 more
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Spontaneous atomic-scale magnetic skyrmion lattice in two dimensions

2011-07-31
Stefan Heinze , Kirsten von Bergmann , Matthias Menzel +5 more

Experimental Confirmation of the X-Ray Magnetic Circular Dichroism Sum Rules for Iron and Cobalt

1995-07-03
C. T. Chen , Y. U. Idzerda , H.‐J. Lin +6 more
High precision, $L$${}_{2,3}$-edge photoabsorption and magnetic circular dichroism spectra of iron and cobalt were measured in transmission with in situ grown thin films, eliminating experimental artifacts encountered by the indirect … High precision, $L$${}_{2,3}$-edge photoabsorption and magnetic circular dichroism spectra of iron and cobalt were measured in transmission with in situ grown thin films, eliminating experimental artifacts encountered by the indirect methods used in all previous measurements. The magnetic moments determined from the integrals of these spectra are found to be in excellent agreement (within 3%) for the orbital to spin moment ratios, and in good agreement (within 7%) for the individual moments, with those obtained from Einstein--de Haas gyromagnetic ratio measurements, demonstrating decisively the applicability of the individual orbital and spin sum rules.

Spin transfer torques

2008-01-27
D. C. Ralph , M. D. Stiles

Oscillations in exchange coupling and magnetoresistance in metallic superlattice structures: Co/Ru, Co/Cr, and Fe/Cr

1990-05-07
S. Parkin , Neha More , K. P. Roche
We report the discovery of antiferromagnetic interlayer exchange coupling and enhanced saturation magnetoresistance in two new metallic superlattice systems, Co/Cr and Co/Ru. In these systems and in Fe/Cr superlattices both … We report the discovery of antiferromagnetic interlayer exchange coupling and enhanced saturation magnetoresistance in two new metallic superlattice systems, Co/Cr and Co/Ru. In these systems and in Fe/Cr superlattices both the magnitude of the interlayer magnetic exchange coupling and the saturation magnetoresistance are found to oscillate with the Cr or Ru spacer layer thickness with a period ranging from 12 \AA{} in Co/Ru to \ensuremath{\simeq}18--21 \AA{} in the Fe/Cr and Co/Cr systems.

A perpendicular-anisotropy CoFeB–MgO magnetic tunnel junction

2010-07-11
Shoji Ikeda , K. Miura , Hirotsugu Yamamoto +7 more

Enhanced Gilbert Damping in Thin Ferromagnetic Films

2002-02-28
Yaroslav Tserkovnyak , Arne Brataas , G. Bauer
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 … 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 constant in the Landau-Lifshitz equation. The damping is expressed in terms of the scattering matrix of the ferromagnetic layer, which is accessible to model and first-principles calculations. Our estimates for permalloy thin films explain the trends observed in recent experiments.
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The design and verification of MuMax3

2014-10-01
Arne Vansteenkiste , Jonathan Leliaert , Mykola Dvornik +3 more
We report on the design, verification and performance of MuMax3, an open-source GPU-accelerated micromagnetic simulation program. This software solves the time- and space dependent magnetization evolution in nano- to micro … We report on the design, verification and performance of MuMax3, an open-source GPU-accelerated micromagnetic simulation program. This software solves the time- and space dependent magnetization evolution in nano- to micro scale magnets using a finite-difference discretization. Its high performance and low memory requirements allow for large-scale simulations to be performed in limited time and on inexpensive hardware. We verified each part of the software by comparing results to analytical values where available and to micromagnetic standard problems. MuMax3 also offers specific extensions like MFM image generation, moving simulation window, edge charge removal and material grains.
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Resistance Minimum in Dilute Magnetic Alloys

1964-07-01
J. Kondo
Based on the s-d interaction model for dilute magnetic alloys we have calculated the scattering probability of the conduction electrons to the second Born approximation. Because of the dynamical character … Based on the s-d interaction model for dilute magnetic alloys we have calculated the scattering probability of the conduction electrons to the second Born approximation. Because of the dynamical character of the localized spin system, the Pauli principle should be taken into account in the intermediate states of the second order terms. Thus the effect of the Fermi sphere is involved in the scattering probability and gives rise to a singular term in the resistivity which involves c log T as a factor, where c is the concentration of impurity atoms. When combined with the lattice resistivity, this gives rise to a resistance minimum, provided the s-d exchange integral J is negative. The temperature at which the minimum ccurs is proportional to c1/5 and the depth of the minimum to c, as is observed. The predicted log T dependence is tested with available experiments and is confirmed. The value of J to have fit with experiments is about -0.2 ev, which is of reasonable magnitude. Our conclusion is that J should be negative in alloys which show a resistance minimum. It is argued that the resistance minimum is a result of the sharp Fermi surface.
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Exchange bias in nanostructures

2005-10-28
J. Nogués , Jordi Sort , V. Langlais +4 more

Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection

2011-07-29
Ioan Mihai Miron , Kévin Garello , Gilles Gaudin +7 more
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Real-space observation of a two-dimensional skyrmion crystal

2010-06-01
Xiuzhen Yu , Y. Onose , Naoya Kanazawa +5 more

Field Dependence of the Intrinsic Domain Magnetization of a Ferromagnet

1940-12-15
T. Holstein , H. Primakoff
In this paper, the variation of the intrinsic domain magnetization of a ferromagnetic with the external magnetic field, is obtained. The basis of the treatment is the exchange interaction model … In this paper, the variation of the intrinsic domain magnetization of a ferromagnetic with the external magnetic field, is obtained. The basis of the treatment is the exchange interaction model amplified by explicit consideration of the dipole-dipole interaction between the atomic magnets. Approximations appropriate to low temperatures and equivalent to those used by Bloch in his derivation of the ${T}^{1}$ law, are introduced. The resultant expression for the intrinsic volume susceptibility decreases slowly with increasing field; at high fields the functional dependence is as the inverse square root of the field. The variation with temperature is linear; at room temperature and for fields of about 4000 gauss, the order of magnitude of the (volume) susceptibility is ${10}^{\ensuremath{-}4}$. The results are compared with experiment and satisfactory agreement is found.

Interaction Between the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>d</mml:mi></mml:math>Shells in the Transition Metals

1951-02-01
Clarence Zener
It is assumed (1) that the interaction between the incomplete $d$ shells of the transition elements is insufficient to disrupt the coupling between the $d$ electrons in the same shells, … It is assumed (1) that the interaction between the incomplete $d$ shells of the transition elements is insufficient to disrupt the coupling between the $d$ electrons in the same shells, and (2) that the exchange interaction between adjacent $d$ shells always has the same sign irrespective of distance of separation. The direct interaction between adjacent $d$ shells then invariably leads to a tendency for an antiferromagnetic alignment of $d$ spins. The body-centered cubic structure of the transition metals V, Cr, Cb, Mo, Ta, and W is thereby interpreted, as well as more complex lattices of certain alloys. It is demonstrated that the spin coupling between the incomplete $d$ shells and the conduction electrons leads to a tendency for a ferromagnetic alignment of $d$ spins. The occurrence of ferromagnetism is thereby interpreted in a much more straightforward manner than through the ad hoc assumption of a reversal in sign of the exchange integral. The occurrence of antiferromagnetism and of ferromagnetism in various systems is readily understood, and certain simple rules are deduced for deciding which type of magnetism will occur in particular alloys.

Spin Hall effects

2015-10-27
Jairo Sinova , Sergio O. Valenzuela , J. Wunderlich +2 more
In solid-state materials with strong relativistic spin-orbit coupling, charge currents generate transverse spin currents. The associated spin Hall and inverse spin Hall effects distinguish between charge and spin current where … In solid-state materials with strong relativistic spin-orbit coupling, charge currents generate transverse spin currents. The associated spin Hall and inverse spin Hall effects distinguish between charge and spin current where electron charge is a conserved quantity but its spin direction is not. This review provides a theoretical and experimental treatment of this subfield of spintronics, beginning with distinct microscopic mechanisms seen in ferromagnets and concluding with a discussion of optical-, transport-, and magnetization-dynamics-based experiments closely linked to the microscopic and phenomenological theories presented.

Anisotropic Superexchange Interaction and Weak Ferromagnetism

1960-10-01
Tôru Moriya
A theory of anisotropic superexchange interaction is developed by extending the Anderson theory of superexchange to include spin-orbit coupling. The antisymmetric spin coupling suggested by Dzialoshinski from purely symmetry grounds … A theory of anisotropic superexchange interaction is developed by extending the Anderson theory of superexchange to include spin-orbit coupling. The antisymmetric spin coupling suggested by Dzialoshinski from purely symmetry grounds and the symmetric pseudodipolar interaction are derived. Their orders of magnitudes are estimated to be ($\frac{\ensuremath{\Delta}g}{g}$) and ${(\frac{\ensuremath{\Delta}g}{g})}^{2}$ times the isotropic superexchange energy, respectively. Higher order spin couplings are also discussed. As an example of antisymmetric spin coupling the case of Cu${\mathrm{Cl}}_{2}$\ifmmode\cdot\else\textperiodcentered\fi{}2${\mathrm{H}}_{2}$O is illustrated. In Cu${\mathrm{Cl}}_{2}$\ifmmode\cdot\else\textperiodcentered\fi{}2${\mathrm{H}}_{2}$O, a spin arrangement which is different from one accepted so far is proposed. This antisymmetric interaction is shown to be responsible for weak ferromagnetism in $\ensuremath{\alpha}$-${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$, MnC${\mathrm{O}}_{3}$, and Cr${\mathrm{F}}_{3}$. The paramagnetic susceptibility perpendicular to the trigonal axis is expected to increase very sharply near the N\'eel temperature as the temperature is lowered, as was actually observed in Cr${\mathrm{F}}_{3}$.

Antiferromagnetic spintronics

2018-02-15
V. Baltz , Aurélien Manchon , Maxim Tsoi +3 more
Spintronics utilizing antiferromagnetic materials has potential for the next generation of applications and offers opportunities for new ideas. Ultimately, antiferromagnets could replace ferromagnets as the active spin-dependent element on which … Spintronics utilizing antiferromagnetic materials has potential for the next generation of applications and offers opportunities for new ideas. Ultimately, antiferromagnets could replace ferromagnets as the active spin-dependent element on which spintronic devices are based. Central to this endeavor is the need for predictive models, relevant disruptive materials, and new experimental designs. This paper reviews spintronic effects described based on theoretical and experimental analysis of antiferromagnetic materials.
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Antiferromagnetic spintronics

2016-03-01
T. Jungwirth , X. Martí , P. Wadley +1 more
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Magnetic skyrmions: advances in physics and potential applications

2017-06-13
A. Fert , Nicolas Reyren , Vincent Cros
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Magnon spintronics

2015-06-01
Andrii V. Chumak , Vitaliy I. Vasyuchka , A. A. Serga +1 more

Exchange bias

1999-02-01
J. Nogués , Iván K. Schuller

Superparamagnetism

1959-04-01
C. P. Bean , J. D. Livingston
Single domain ferromagnetic particles at elevated temperatures can behave magnetically in a manner analogous to the Langevin paramagnetism of moment-bearing atoms. The main distinction is that the moment of the … Single domain ferromagnetic particles at elevated temperatures can behave magnetically in a manner analogous to the Langevin paramagnetism of moment-bearing atoms. The main distinction is that the moment of the particle may be 105 times the atomic moment. The experimental and theoretical foundations of this effect are reviewed and indication is made of the applications of this phenomenon. Lastly, attention is drawn to some current problems in this area.

Magnetoelectronics

1998-11-27
G. A. Prinz
An approach to electronics is emerging that is based on the up or down spin of the carriers rather than on electrons or holes as in traditional semiconductor electronics. The … An approach to electronics is emerging that is based on the up or down spin of the carriers rather than on electrons or holes as in traditional semiconductor electronics. The physical basis for the observed effects is presented, and the initial successful applications of this technology for information storage are reviewed. Additional opportunities for the exploitation of this technology, which are currently under study, are described.

Tunable Magnetism in 2D XI₂ (X = Fe, Co, Ni) Monolayers: The Potential Toward Room-Temperature Functional Spintronic Materials

2025-06-24
Wei Han , Haopeng Zhang , Ying Liu +5 more | Physica Scripta
Abstract Two-dimensional (2D) materials with room-temperature magnetism and large magnetic anisotropy energy (MAE) are essential for advancing next-generation nanoscale spintronic devices. In this work, we systematically investigate the structural, magnetic, … Abstract Two-dimensional (2D) materials with room-temperature magnetism and large magnetic anisotropy energy (MAE) are essential for advancing next-generation nanoscale spintronic devices. In this work, we systematically investigate the structural, magnetic, and electronic properties of XI2 (X = Fe, Co, Ni) monolayers based on first-principles calculations. In all three materials, the transition metal atoms occupy the centers of hexagonal rings and are coordinated by iodine atoms in a hexagonal geometry. Among them, CoI2 exhibits a Curie temperature as high as 320 K, indicating promising room-temperature ferromagnetism. All three monolayers exhibit relatively large MAE values, with NiI2 showing the largest, primarily due to strong spin-orbit coupling and pronounced orbital hybridization between Ni-3d and I-5p orbitals. The easy magnetization axis lies in-plane for FeI2 and CoI2, and out-of-plane for NiI2. Under biaxial strains ranging from −3% to +3%, FeI2 and NiI2 retain their antiferromagnetic (AFM) and ferromagnetic (FM) ground states, respectively, demonstrating robust magnetic phase stability. In contrast, CoI2 undergoes a strain-induced transition between FM and AFM states, offering a pathway to strain-tunable magnetism. Furthermore, ab initio molecular dynamics(AIMD) simulations confirm the thermodynamic stability of FeI2 up to 1000 K. These combined features—high Curie temperature, large MAE, and excellent thermal and magnetic robustness—highlight XI2 monolayers as promising candidates for future nanoscale spintronic applications.

Magnetic shape anisotropy of high-axial-ratio cobalt nanoparticles in nanogranular films

2025-06-23
Hanae Kijima-Aoki , Tetsuroh Kawai , Yang Cao +4 more | Journal of Applied Physics
Magnetic shape anisotropy is a principle guiding the nano-scale design of magnetic hetero-structures against competitive thermal fluctuation. Here, we have fabricated self-organized nanogranular films comprising ellipsoidal ferromagnetic nanoparticles with a … Magnetic shape anisotropy is a principle guiding the nano-scale design of magnetic hetero-structures against competitive thermal fluctuation. Here, we have fabricated self-organized nanogranular films comprising ellipsoidal ferromagnetic nanoparticles with a wide range of aspect ratios from 0.6 to 6.1. Designed to have a significantly higher anisotropy field greater than 100 mT, these particles are not magnetically coupled with a single-domain state. Such a structure allows the coherent rotation of magnetization with respect to the particle axial ratio alone. Thanks to its shape anisotropy, the thermal stability of ferromagnetism in the ellipsoidal particle is several hundred kelvins greater than that of the sphere case. Enhanced thermal stability yields nanoscale hard magnetism seamlessly integrated with the matrix's dielectric and optical functions, paving the way for next-generation integrated nanosystems.

Er-driven magnetic tunability in FePt thin films investigated via high-throughput experiments and microstructure analysis for future HAMR media

2025-06-23
Daisuke Ogawa , Yuma Iwasaki , Jun Uzuhashi +3 more | Applied Physics Letters
This study undertakes comprehensive experimental validations based on theoretical predictions of the impact of Er and Tm doping on the magnetic properties of FePt thin films. Initial theoretical investigations indicate … This study undertakes comprehensive experimental validations based on theoretical predictions of the impact of Er and Tm doping on the magnetic properties of FePt thin films. Initial theoretical investigations indicate that doping with rare earth elements may result in promising alterations to the magnetic properties of the FePt thin films, with Er doping in particular offering a promising avenue for further study. Experimental synthesis via a combinatorial high-throughput sputtering system, which enables precise control over the composition of FePt thin films, achieves the desired magnetic properties. Small quantities of dopants, specifically 0.35 at. % Er, substantially enhance the key magnetic properties of saturation magnetization (μ0Ms), anisotropy constant (Ku) at room temperature, and the Curie temperature (TC). Precise microstructural observations of a sample show that Er segregates at grain boundaries, voids, and the substrate/FePt interface, where Er preferentially replaces Fe sites. In other regions of the FePt grains, Er is not solid-soluble, and pure FePt and FePtEr form a composite material in the order of tens of nm. The incorporation of Er also influences the damping constant α. The findings of this study substantiate the intrinsic characteristics of Er-doped films, particularly the enhanced μ0Ms, Ku, and TC attainable with nominal dopant concentrations, and facilitate the realization of ultimate magnetic recording densities anticipated for future data storage technologies.

Sign reversal of spin–orbit torque induced by interfacial antiferromagnetic coupling

2025-06-23
Yuanjing Qu , Xinkai Xu , Zhiyong Zhong +4 more | Applied Physics Letters
Nonmagnetic-metal/ferromagnetic heterostructures have drawn extensive attention due to the generation of spin–orbit torque (SOT). This work is based on the large spin Hall angle observed in Pt0.70(GdOy)0.30 composite films, we … Nonmagnetic-metal/ferromagnetic heterostructures have drawn extensive attention due to the generation of spin–orbit torque (SOT). This work is based on the large spin Hall angle observed in Pt0.70(GdOy)0.30 composite films, we focus on investigating the sharp sign reversal of the damping-like SOT induced by antiferromagnetic coupling at the NiFe/Pt1−x(GdOy)x (x ≥ 0.30) interface. Such interface-modulated SOT is found to be suppressed by inserting an ultra-thin copper spacer layer using spin-torque ferromagnetic resonance. Meanwhile, the relevant interfacial parameters further indicate the key importance of interfacial magnetic coupling for boosting spin transport efficiency. The superconducting quantum interference device tests on NiFe/Pt1−x(GdOy)x (x ≥ 0.30) structures reveal that the magnetization in Pt1−x(GdOy)x is antiparallel to that of NiFe, forming an antiferromagnetically coupled configuration at the NiFe/Pt1−x(GdOy)x interface. Our results highlight the promising application of rare earth materials in spin transport, and the construction of interfacial antiferromagnetic coupling opens a route to modulate SOT.

Deformation and motion of skyrmion bags driven by surface acoustic wave

2025-06-23
Shengbin Shi , Yunhong Zhao , Peng Han +3 more | Applied Physics Letters
Skyrmion bags are stable spin textured topologies with arbitrary topological charges, and have the potential to become new carriers in racetrack memory. After the discovery of skyrmion bags, the injection … Skyrmion bags are stable spin textured topologies with arbitrary topological charges, and have the potential to become new carriers in racetrack memory. After the discovery of skyrmion bags, the injection and driving methods of a single skyrmion are gradually applied to the manipulation of skyrmion bags. However, traditional methods, including spin current, magnetic anisotropic gradient, and spin waves generated by microwave fields, inevitably bring problems of high energy consumption and difficulty in miniaturization. With the development of strain electronics, acoustic waves have been widely used to manipulate magnetic topologies. Here, we numerically investigate the dynamical characteristic of skyrmion bags driven by surface acoustic waves. The results show that material damping and acoustic wave amplitude and frequency have a great influence on the skyrmion bag. With decrease in damping, the skyrmion bags move gradually faster. Also, increase in amplitude or frequency can generate similar effect on the velocity of skyrmion bags. Unlike acoustic wave-driven single skyrmions, the strong magnetoelastic coupling effect in the ferromagnetic film and the rich spin texture of skyrmion bags induce deformation in the skyrmion, along with a 38% increase in its velocity. Further, the deformation of the skyrmion is a combined effect of in situ rotation and breath caused by surface acoustic waves. This work demonstrates that the surface acoustic wave can be used to drive skyrmion bags, which offers potential applications for diverse storage of information based on the skyrmion bags in the future.

Dzyaloshinskii‐Moriya Interactions Driven Field‐Free Magnetization Switching in Perpendicular <i>L</i>1<sub>0</sub>‐FePt Single Films with Crystal Phase Gradient

2025-06-23
Yuanbo Wang , Jingyan Zhang , Jianying Zhang +7 more | Advanced Functional Materials
Abstract Dzyaloshinskii‐Moriya interaction (DMI) enables the formation of various topological magnetic structures and efficient manipulation of magnetization switching for advanced‐generation spintronic devices. It is shown that the existence of DMI … Abstract Dzyaloshinskii‐Moriya interaction (DMI) enables the formation of various topological magnetic structures and efficient manipulation of magnetization switching for advanced‐generation spintronic devices. It is shown that the existence of DMI is strongly related to the interfacial nature and compositional distribution in magnetic films. However, evidence that DMI is induced by the crystal structure of magnetic materials is still lacking thus far. Herein, a crystal phase gradient is porposed to induce bulk DMI in L 1 0 ‐FePt films with homogeneous composition by introducing an artificial ordering degree gradient ( ΔS ) along the film normal. The DMI constant can be effectively tuned by adjusting the magnitude of ΔS of the L 1 0 ‐FePt films, which can successfully realize field‐free magnetization switching with a significant improvement in spin‐orbit torque (SOT) efficiency. The vertical difference in ΔS , which is confirmed by structural characteristics, leads to magnetic inhomogeneity, as evidenced by polarized neutron reflectometry. In addition, experimental and simulation results show that asymmetrical domain walls, arising from the interplay of bulk DMI and magnetic inhomogeneity, generate an out‐of‐plane effective field, leading to deterministic magnetization switching. These findings provide an innovative strategy for the realization chiral interactions through atomic occupy engineering that facilitates the development of SOT‐based spintronic devices.

Unveiling the 3D Spin Texture of Nanowires Using Integrated Microscopy Techniques

2025-06-22
Claudia Fernández-González , Laura Álvaro-Gómez , Laura Fernández-García +7 more | Nano Letters
This study integrates multiple microscopy techniques to investigate the effect of introducing axial compositional gradients on the magnetic properties of Fe-Ni ferromagnetic nanowires. We study the chemical structure of the … This study integrates multiple microscopy techniques to investigate the effect of introducing axial compositional gradients on the magnetic properties of Fe-Ni ferromagnetic nanowires. We study the chemical structure of the nanowires using photoemission electron microscopy and transmission (X-ray and electron) microscopy. We explore the magnetic properties through magnetic force microscopy, complemented by micromagnetic simulations, and we characterize the 3D magnetization vector by measuring magnetic circular dichroism using X-ray microscopies. We observe that variations in the Fe/Ni ratio induce localized magnetic curling in Fe-rich regions, while Ni-rich segments predominantly exhibit axial magnetization, demonstrating how compositional gradients can control magnetic domain configurations on the nanoscale. Our results highlight the value of multimodal imaging for uncovering the interplay among structural, chemical, and magnetic properties in complex nanostructures. These findings represent a significant step toward the manipulation of magnetic domains in nanowires, which is essential for future devices based on 3D nanomagnetic architectures.

NeuralMag: an open-source nodal finite-difference code for inverse micromagnetics

2025-06-21
Claas Abert , Florian Bruckner , А. В. Воронов +7 more | npj Computational Materials
We present NeuralMag, a flexible and high-performance open-source Python library for micromagnetic simulations. NeuralMag leverages modern machine learning frameworks, such as PyTorch and JAX, to perform efficient tensor operations on … We present NeuralMag, a flexible and high-performance open-source Python library for micromagnetic simulations. NeuralMag leverages modern machine learning frameworks, such as PyTorch and JAX, to perform efficient tensor operations on various parallel hardware, including CPUs, GPUs, and TPUs. The library implements a novel nodal finite-difference discretization scheme that provides improved accuracy over traditional finite-difference methods without increasing computational complexity. NeuralMag is particularly well-suited for solving inverse problems, especially those with time-dependent objectives, thanks to its automatic differentiation capabilities. Performance benchmarks show that NeuralMag is competitive with state-of-the-art simulation codes while offering enhanced flexibility through its Python interface and integration with high-level computational backends.
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Probing polarization-tunable sub-terahertz spin pumping in bimodal α-Fe2O3/Pt

2025-06-20
Gregory Fritjofson , Atul Regmi , Jacob Hanson-Flores +5 more | npj Spintronics

Electrical detection of interfacial exchange field at the (ferromagnetic insulator)|(normal metal) interface using spin-dependent scattering

2025-06-20
P. K. Muduli , Naëmi Leo , Mingran Xu +5 more | Journal of Physics D Applied Physics
Abstract The spin-orbit field and interfacial exchange field are two major interface phenomena, and the detection and manipulation of these fields can enable a variety of nanoscale spintronics devices. Optimizing … Abstract The spin-orbit field and interfacial exchange field are two major interface phenomena, and the detection and manipulation of these fields can enable a variety of nanoscale spintronics devices. Optimizing the interfacial exchange field, which governs the spin-dependent scattering asymmetry at (ferromagnetic insulator)-(normal metal) interfaces, will pave the way for next-generation nanoscale, low-power insulator spintronics devices. Here, we demonstrate an experimental pathway to detect an interfacial exchange field between insulating ferromagnet EuS and non-magnetic Cu using magnetoresistance measurements, and show that the spin-dependent scattering at the common interface can lead to a significant current-in-plane magnetoresistance in Py|Cu|EuS trilayer Hall-bar device. Our experiment suggests that simple measurements can be used to experimentally detect the interfacial exchange field and thereby the magnetic state of a ferromagnetic insulator.
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Perpendicular magnetic anisotropy in a single Dy adatom ferrimagnet

2025-06-20
A. B. Shick , F. Máca , I. Halevy +1 more | Research Square (Research Square)
<title>Abstract</title> The electronic structure and magnetism of individual Dy atoms adsorbed on ferromagnetic (Gr)/Ni(111) substrate are investigated using a combination of the density functional theory with the Hubbard-I approximation to … <title>Abstract</title> The electronic structure and magnetism of individual Dy atoms adsorbed on ferromagnetic (Gr)/Ni(111) substrate are investigated using a combination of the density functional theory with the Hubbard-I approximation to the Anderson impurity model (DFT+U(HIA)). The divalent Dy2+ adatom in f10 configuration with [J = 8, L=6, S=2] is found. The values of spin MS=3.4 mB, orbital ML=5.2 mB, and total MJ=8.6 mB magnetic moments calculated for the Dy f-shell are noticeably different from the atomic second Hund's rule. There is almost zero moment on (Gr)-atoms. The ferromagnetic Ni substrate moments are anti-aligned to the Dy 4f-shell moment. The X-ray absorption (XAS) and magnetic circular dichroism (XMCD) spectra are calculated and can be compared to the experimental data. The magnetic anisotropy energy (MAE) is calculated from the ground state energy difference for different directions of the magnetization, E[100] - E[001] = 2.8 meV and E[010] - E[001] = 2.2 meV. This large and positive MAE can be important for ultra-high density magnetic recording. The magnetization of Dy@(Gr)/Ni(111) is tilted with respect to the (Gr)/Ni(111) substrate normal by 38o due to a competition between negative first and third order magnetic anisotropies and strong and positive second order magnetic anisotropies. Our studies assist in resolving ambiguities of conventional DFT+U applied to Dy on graphene. They can provide a viable route for further investigation and prediction of the rare-earth based magnetic nanostructures.

Interlayer Dzyaloshinskii-Moriya interaction in spintronics

2025-06-20
Xupeng Zhao , Jianhua Zhao | npj Spintronics

WinEdge: Low-Power Winograd CNN Execution with Transposed MRAM for Edge Devices

2025-06-19
Milad Ashtari Gargari , Sepehr Tabrizchi , Arman Roohi | Electronics
This paper presents a novel transposed MRAM architecture (WinEdge) specifically optimized for Winograd convolution acceleration in edge computing devices. Leveraging Magnetic Tunnel Junctions (MTJs) with Spin Hall Effect (SHE)-assisted Spin-Transfer … This paper presents a novel transposed MRAM architecture (WinEdge) specifically optimized for Winograd convolution acceleration in edge computing devices. Leveraging Magnetic Tunnel Junctions (MTJs) with Spin Hall Effect (SHE)-assisted Spin-Transfer Torque (STT) writing, the proposed design enables a single SHE current to simultaneously write data to four MTJs, substantially reducing power consumption. Additionally, the integration of stacked MTJs significantly improves storage density. The proposed WinEdge efficiently supports both standard and transposed data access modes regardless of bit-width, achieving up to 36% lower power, 47% reduced energy consumption, and 28% faster processing speed compared to existing designs. Simulations conducted in 45 nm CMOS technology validate its superiority over conventional SRAM-based solutions for convolutional neural network (CNN) acceleration in resource-constrained edge environments.

Tailoring Antiferromagnetic Orders and Spin Transport in Noncollinear Mn<sub>3</sub>Pt Multilayers

2025-06-19
Shaohai Chen , B. C. Lim , Dennis J. X. Lin +7 more | Advanced Functional Materials
Abstract Noncollinear antiferromagnetic (NCAF) materials, such as Mn₃Pt, exhibit remarkable spin‐orbit and tunneling phenomena, positioning them as promising candidates for low‐power, stray‐field immune nanoelectronics. However, precise control of AF order … Abstract Noncollinear antiferromagnetic (NCAF) materials, such as Mn₃Pt, exhibit remarkable spin‐orbit and tunneling phenomena, positioning them as promising candidates for low‐power, stray‐field immune nanoelectronics. However, precise control of AF order and spin transport properties, and understanding of their physical mechanisms, remains challenging. In this work, the interplay between crystal structure, magnetic orders, and anomalous Hall effect (AHE) is established in single‐crystalline Mn₃Pt (001) synthesized from a [Mn/Pt] 20 multilayers with tunable Mn layer thickness ( t Mn ). Resonant elastic X‐ray scattering reveals a magnetic order transition at T c ≈240 K for the sample with t Mn = 0.7 nm, which notably coincides with an AHE polarity reversal at ≈230 K. Importantly, we demonstrate that T c can be precisely engineered by fine‐tuning t Mn to modulate lattice constant and spin canting. Further, first‐principles calculations affirm the lattice parameter and spin canting dependence of AHE from the ground‐state Γ 10 magnetic symmetry. Finally, a refined analytical model is introduced to elucidate the intrinsic and extrinsic AHE contributions in NCAF material comprising hybrid magnetic orders. These findings provide a robust framework for tailoring transport properties toward the realization of next‐generation AF computing technologies.

Electronic structures of NANOMET-based nanocrystalline soft magnetic Alloys: Magnetic properties

2025-06-18
J.M. Park , Minyeong Choi , Hyunkyung Lee +4 more | Physica B Condensed Matter

Magnetoresistance in Co/Cu superlattices with specular surfaces and well-formed interfaces

2025-06-17
Bassem Elsafi | Applied Physics A

Dynamical Simulation of Chiral-Induced Spin-Polarization and Magnetization

2025-06-17
Pengyi Liu , Tian-Yi Zhang , Qing‐Feng Sun | The Journal of Physical Chemistry Letters
Despite generally lacking ferromagnetic properties or strong spin-orbit coupling, electrons in chiral molecules exhibit unique spin-dependent transport behavior, known as chiral-induced spin selectivity (CISS). This phenomenon implies a profound connection … Despite generally lacking ferromagnetic properties or strong spin-orbit coupling, electrons in chiral molecules exhibit unique spin-dependent transport behavior, known as chiral-induced spin selectivity (CISS). This phenomenon implies a profound connection between chirality and spin and draws attention to the link between chirality and magnetism. Experiments in recent years have shown that chirality can induce spin-polarizations and magnetizations, providing fresh insights into interpreting chirality-related biochemical processes and designing nanomagnetic devices. In this Letter, we present a dynamical theoretical model aimed at elucidating how charge-polarization combined with the CISS leads to spin-polarization and magnetization. Our theoretical model successfully explains the spin-polarization and magnetization observed in three types of experiments, where charge-polarization is induced in the chiral molecules by the dispersion interaction, gate voltage, and molecular adsorption. The model simulates a clear time evolution process and provides a comprehensive theoretical framework for this field.

Magnetic Field Switching of Exchange Bias in a Metallic FM/AFM Heterostructure at Room Temperature

2025-06-17
Mihiro Asakura , Tomoya Higo , Takumi Matsuo +5 more | Nano Letters
The exchange bias effect, which causes a shift in the ferromagnetic hysteresis loop due to magnetic coupling with an adjacent antiferromagnetic layer, has been a key area of study for … The exchange bias effect, which causes a shift in the ferromagnetic hysteresis loop due to magnetic coupling with an adjacent antiferromagnetic layer, has been a key area of study for fundamental research and spintronic applications. This effect is known to be static once established through a field cooling procedure and is difficult to manipulate isothermally. Here we present the first room temperature field switching of interlayer magnetic coupling at the metallic heterointerface between a ferromagnet and antiferromaget. Specifically, we demonstrate that the exchange bias can be systematically switched by manipulating the global time-reversal-symmetry-broken antiferromagnetic order of Mn3Sn via both magnetic field sweeping and field cooling. Furthermore, we confirm that the magnitude and sign of the interlayer coupling can be tuned by selecting the ferromagnet. These findings provide a novel approach for controlling the magnetic state of ferromagnets and functional antiferromagnets, paving the way for advancing spintronic technologies using antiferromagnets.

Switching a chiral antiferromagnet

2025-06-16
Simranjeet Singh , I-Hsuan Kao | Nature Materials

Ultrafast spin dynamics and spin transport in ferromagnetic spin valve

2025-06-16
В. Н. Гриднев | Journal of Magnetism and Magnetic Materials

Parametric magnon-driven anisotropic spin pumping

2025-06-16
Sourabh Manna , Rohit Medwal , John Rex Mohan +6 more | Applied Physics Letters
We explore the effect of magnetic anisotropy on the interplay between spin current and parametric instability in magnetization dynamics, crucial for developing efficient nonlinear spintronics devices. The parametric instability is … We explore the effect of magnetic anisotropy on the interplay between spin current and parametric instability in magnetization dynamics, crucial for developing efficient nonlinear spintronics devices. The parametric instability is induced by the Suhl process where a uniform mode magnon excites two counter-propagating parametric magnons. We experimentally demonstrate direction-specific spin current generation via spin pumping from these parametrically excited magnons in a thin bilayer of [110]-oriented yttrium iron garnet and platinum (Pt), utilizing the facet-dependent magnetocrystalline anisotropy and magnetodipolar interaction. The facet-symmetry and the shape anisotropy modulate the magnonic dispersion relation as well as the magnon-scattering process which determines the spin pumping efficiency. Analyzing the in-plane angular dependence of spin pumping-induced inverse spin Hall effect voltage, we demonstrate anisotropic control of the spin pumping efficiency of the parametric magnons. Our findings provide critical insights to enhance control in magnonic logic devices.

Half-metallic Fe/MgO superlattice: An ideal candidate for magnetic tunnel junction electrodes

2025-06-16
Nicholas A. Lanzillo , Sergey V. Faleev , Aakash Pushp | Applied Physics Letters
Magnetic tunnel junction (MTJ) based spin-transfer torque magnetic random access memory is poised to replace embedded Flash for advanced applications such as automotive microcontroller units. To achieve deeper technological adoption, … Magnetic tunnel junction (MTJ) based spin-transfer torque magnetic random access memory is poised to replace embedded Flash for advanced applications such as automotive microcontroller units. To achieve deeper technological adoption, MTJ needs to exhibit three key features: low magnetization (Ms), high perpendicular magnetic anisotropy, and high tunnel magnetoresistance (TMR). Here, we theoretically show that when Fe/MgO multilayers are inserted into the fixed and free layers of the MTJ, these three conditions are simultaneously met. As the number of Fe/MgO multilayers in MTJ electrodes is increased, we find that the electron transport evolves from direct barrier tunneling of majority spin states to the resonant tunneling of minority spin states. Remarkably, the projected density of states (PDOS) of the Fe/MgO superlattice at the MgO tunnel barrier exhibits half-metallicity near the Fermi energy, where the minority states exist while the majority states are gapped out, resulting in astronomically high TMR.

Fast reversal of Néel vectors in antiferromagnets via domain-wall motion driven by vertically injected spin currents

2025-06-16
Jiaxin Du , Mei Li , Bin Xi +4 more | Applied Physics Letters
In this work, we investigate the steady propagation of 180-degree domain walls (180DWs) of Néel vectors in thin antiferromagnetic strips under vertically injected spin currents with various polarization orientations. Our … In this work, we investigate the steady propagation of 180-degree domain walls (180DWs) of Néel vectors in thin antiferromagnetic strips under vertically injected spin currents with various polarization orientations. Our results show that only spin currents polarized parallel to the hard axis guarantee a quick and steady rigid flow of 180DWs, thus realize a fast reversal of Néel vectors in antiferromagnets (AFMs). Different from the common “current-in-plane” geometry, which is feasible only for metallic AFMs, our “current-out-of-plane” layout under investigation can further apply to insulating or semiconducting AFMs (which are more common in real applications) via quantum tunneling effect. The results from this work pave the way for fine control of Néel vectors in strip-shaped AFMs and further development of magnetic nanodevices based on them.

Quantification of magnetization of nanostructures via three complementary methods

2025-06-16
Xianhui Ye , Hangbo Su , Jiaqi Su +4 more | Applied Physics Letters
The quantitative measurement of magnetization in magnetic nanostructures plays a crucial role in advancing both fundamental understanding and applied research. Off-axis electron holography in a transmission electron microscope enables the … The quantitative measurement of magnetization in magnetic nanostructures plays a crucial role in advancing both fundamental understanding and applied research. Off-axis electron holography in a transmission electron microscope enables the retrieval of magnetic phase shifts induced by magnetic induction fields, thereby allowing precise quantification of magnetization. Using magnetite (Fe3O4) nanoparticles as a model system, we use off-axis electron holography to demonstrate three complementary methods for quantifying the magnetic properties of nanoparticles. These methods are the simple geometric approximation, the magnetic phase gradient integration, and the model-based iterative reconstruction, each providing unique capability, ranging from the rapid estimation of in-plane magnetic induction to highly detailed spatially resolved magnetization maps. We analyze the strengths, the limitations, and the applicability of each approach, emphasizing the potential of integrating these methods for a comprehensive analysis of the magnetization of nanomaterials.

Improving the Gain and Bandwidth of CMOS Circuits with Fe-MgO Tunnel Junctions

2025-06-15
Mayank Chakraverty , V. N. Ramakrishnan | Electronics ETF
This paper reports the influence of magnetic tunnel junctions on the electrical response of an operational amplifier (op-amp) circuit. As a baseline, the pure-CMOS operational amplifier has been designed using … This paper reports the influence of magnetic tunnel junctions on the electrical response of an operational amplifier (op-amp) circuit. As a baseline, the pure-CMOS operational amplifier has been designed using the 180 nm semiconductor process technology from the Taiwan Semiconductor Manufacturing Company Ltd. and the test bench has been simulated to obtain circuit performance metrics like open loop gain, phase, bandwidth and phase margin. The introduction of a magnetic element can upset the electrical behavior and the same has been observed with the introduction of Fe-MgO tunnel junction on the baseline electrical behavior of the operational amplifier test bench. Possibilities of connecting the tunnel junction to the different nodes of the opamp test bench have been explored and the consequent drifts in the electrical response have been studied in this paper. Furthermore, an attempt has been made to mirror the transistors in the op-amp circuit with tunnel junctions and the consequent electrical responses have been studied in this paper. Such a magneto-CMOS hybrid circuit configuration can be used for a wide range of novel applications that demand a higher packing density in limited die area.

Ferroelectric antiferromagnetic lifting of spin-valley degeneracy

2025-06-15
NULL AUTHOR_ID | Physical review. B./Physical review. B

Multistability and skyrmion annihilation mechanisms in nanodots near ordering temperature

2025-06-13
Xuejin Wan , Yangfan Hu , Biao Wang | Communications Physics

Spin Currents and Torques in Ferromagnetic Systems with Strong Interfacial Spin-Orbit Coupling

2025-06-13
Nils Petter Jørstad , Bernhard Pruckner , Wolfgang Goes +2 more | Research Square (Research Square)
<title>Abstract</title> A three-dimensional description of spin-dependent current transport across nonmagnetic/ferromagnetic interfaces with strong interfacial spin-orbit coupling is presented. The resulting current-induced torques acting on the magnetization of the ferromagnetic layer … <title>Abstract</title> A three-dimensional description of spin-dependent current transport across nonmagnetic/ferromagnetic interfaces with strong interfacial spin-orbit coupling is presented. The resulting current-induced torques acting on the magnetization of the ferromagnetic layer are addressed. By considering both magnetic exchange and Rashba spin-orbit interactions at the interface, the angular dependence of the spin-orbit torques in Pt/Co and Ta/CoFeB systems is reproduced. In line with two-dimensional Rashba models, the Rashba-Edelstein effect drives the strong field-like torque, with the unconventional angular dependence being most pronounced, when magnetic exchange and spin-orbit interaction strengths are comparable. Furthermore, the spin currents generated through spin-orbit precession and filtering are shown to produce all three spin-polarization components, depending on the magnetization direction. Utilizing these mechanisms in current-in-plane trilayers could potentially enable field-free perpendicular and type-x switching, which is crucial for advancing the miniaturization of spintronic devices.

Coupling of magnon modes in nanodisk with spin texture

2025-06-13
ZIQING zhou , Junning Zhao , Xin Ma +2 more | Chinese Physics B
Abstract Magnetic nanostructures with nonhomogeneous magnetic properties would exhibit distinct magnon modes, and their interactions are crucial for understanding the magnetization dynamic behaviors. In this work, we numerically investigate the … Abstract Magnetic nanostructures with nonhomogeneous magnetic properties would exhibit distinct magnon modes, and their interactions are crucial for understanding the magnetization dynamic behaviors. In this work, we numerically investigate the magnon-magnon coupling in nanodisk with radially varying magnetic anisotropy by using micromagnetic simulation. By introducing perpendicular magnetic anisotropy into the inner region of the nanodisk, a radially chiral spin texture is observed. The presence of chiral spin texture results in the coupling between the ferromagnetic resonance mode of the whole disk and the high order confined modes of the outer region. Moreover, we found that the coupling strength is highly sensitive to the perpendicular magnetic anisotropy, the saturation magnetization, and the interfacial Dzyaloshinskii-Moriya interaction. Our findings could enrich the dynamic characters of chiral nanomagnets and suggest a scenario of harnessing tunable magnon-magnon coupling for spin-based quantum information processing.

Controlling the domain wall dynamics in Co-rich magnetic microwires with graded magnetic anisotropy

2025-06-13
Paula Corte-León , V. Zhukova , J.M. Blanco +1 more | Journal of Science Advanced Materials and Devices

Spin-polarized electronic structure of tetragonally distorted FeCo thin films on Rh(001) exhibiting perpendicular magnetic anisotropy

2025-06-12
Kazuya Kunitomo , Kazuki Sumida , K. Miyamoto +1 more | Physical Review Materials

Spinterface-Mediated Magnetic Properties of Nanoscale-Thick Co<sub>20</sub>Fe<sub>60</sub>B<sub>20</sub>/Alq<sub>3</sub> Heterostructures for Spintronic Applications

2025-06-10
Swayang Priya Mahanta , Antarjami Sahoo , Aritra Mukhopadhyaya +5 more | ACS Applied Nano Materials

Néel vector rotation driven by spin–orbit torque in amorphous ferrimagnetic GdCo

2025-06-09
Tetsuma Mandokoro , Yoichi Shiota , Tomoya Itoh +5 more | Applied Physics Letters
Spin superfluidity, a phenomenon enabling low-dissipative spin transport, has remained a theoretical concept. To realize spin superfluidity in an antiferromagnet, it is necessary to excite a Néel vector rotation within … Spin superfluidity, a phenomenon enabling low-dissipative spin transport, has remained a theoretical concept. To realize spin superfluidity in an antiferromagnet, it is necessary to excite a Néel vector rotation within the magnetic easy-plane, which has been elusive so far due to the large magnetocrystalline anisotropy of antiferromagnets. In this study, we demonstrated spin–orbit torque-driven Néel vector rotation in amorphous ferrimagnetic GdCo. A pseudo-magnetic easy-plane is formed in a spin-flop state under an external magnetic field in the vicinity of the magnetization compensation temperature, and we observed stochastic binary switching in the anomalous Hall resistance, directly attributed to Néel vector rotation. Furthermore, homodyne detection confirmed rotation frequencies in the GHz range as expected from atomic spin simulations, providing evidence of dynamic Néel vector behavior. These findings demonstrate the continuous rotation of Néel vector driven by spin–orbit torque.

Perpendicularly magnetized synthetic antiferromagnetic Mn<i>x</i>Ga/Co2FeAl bilayers on MgAl2O4 substrate

2025-06-09
Rongkun Han , Fengyue He , Dong Pan +2 more | Applied Physics Letters
Magnetic tunneling junctions (MTJs) with MgAl2O4 (MAO) barrier exhibit large tunnel magnetoresistance, comparable to that of MgO barrier. In this study, we grow synthetic antiferromagnetic MnxGa/Co2FeAl (CFA) bilayers on MAO … Magnetic tunneling junctions (MTJs) with MgAl2O4 (MAO) barrier exhibit large tunnel magnetoresistance, comparable to that of MgO barrier. In this study, we grow synthetic antiferromagnetic MnxGa/Co2FeAl (CFA) bilayers on MAO (001) substrates without any buffer layer, where the MnxGa layer includes D022-Mn3Ga and L10-MnGa phases. Our results indicate that the CFA forms antiferromagnetic coupling with both D022-Mn3Ga and L10-MnGa. Moreover, we observe the perpendicular magnetic anisotropy (PMA) in both L10-MnGa/CFA and D022-Mn3Ga/CFA bilayers, which is induced by tetragonal MnxGa and interfacial magnetic coupling. Particularly, the L10-MnGa(10 nm)/CFA(1.5 nm) bilayer exhibits a perpendicular anisotropy field of 72.08 kOe and a perpendicular anisotropy energy of 7.57 × 106 erg/cm3. Similar PMA is also observed in L10-MnGa/Co2MnAl and L10-MnGa/Co2FeGa bilayers on MAO substrates. These results provide a foundation for the development of high-performance perpendicular MTJs with MAO barrier.