Large antisymmetric interlayer exchange coupling enabling perpendicular magnetization switching by an in-plane magnetic field

Masuda, Hiroto*; Seki, Takeshi*; Yamane, Yuta*; Modak, R.*; Uchida, Kenichi*; Ieda, Junichi; Lau, Y.-C.*; Fukami, Shunsuke*; Takanashi, Koki

Physical Review Applied (Internet), 17(5), p.054036_1 - 054036_9, 2022/05

https://doi.org/10.1103/PhysRevApplied.17.054036

The antisymmetric interlayer exchange coupling (AIEC) was recently discovered, playing pivotal roles in magnetization switching of a synthetic antiferromagnet (SAF) through inducing magnetization canting. Large AIEC is reported for perpendicularly magnetized Pt/Co/Ir/Co/Pt with wedge-shaped layers. The effective field of the AIEC is related with symmetric interlayer exchange coupling, providing guides to enhance the AIEC. We develop an extended Stoner-Wohlfarth model for a SAF, revealing key factors in its magnetization switching. Combining the theoretical knowledge and the experimental results, perpendicular magnetization switching is achieved solely by an in-plane magnetic field.

Theory of Emergent Inductance with Spin-Orbit Coupling Effects

Yamane, Yuta*; Fukami, Shunsuke*; Ieda, Junichi

Physical Review Letters, 128(14), p.147201_1 - 147201_6, 2022/04

https://doi.org/10.1103/PhysRevLett.128.147201

We extend the theory of emergent inductance, which has recently been discovered in spiral magnets, to arbitrary magnetic textures by taking into account spin-orbit couplings arising in the absence of spatial inversion symmetry. We propose a new concept of spin-orbit emergent inductance, which can be formulated as originating from a dynamical Aharonov-Casher phase of an electron in ferromagnets. The spin-orbit emergent inductance universally arises in the coexistence of magnetism and the spin-orbit couplings, even with spatially uniform magnetization, allowing its stable operation in wide ranges of temperature and frequency. Revisiting the widely studied systems involving ferromagnets with spatial inversion asymmetry, with the new perspective offered by our work, will lead to opening a new paradigm in the study of spin-orbit physics and the spintronics-based power management in ultrawideband frequency range.

Correlation of anomalous Hall effect with structural parameters and magnetic ordering in MnSn thin films

Yoon, J.-Y.*; Takeuchi, Yutaro*; DuttaGupta, S.*; Yamane, Yuta*; Kanai, Shun*; Ieda, Junichi; Ohno, Hideo*; Fukami, Shunsuke*

AIP Advances (Internet), 11(6), p.065318_1 - 065318_6, 2021/06

https://doi.org/10.1063/5.0043192

Skyrmion-generated spinmotive forces in inversion broken ferromagnets

Yamane, Yuta*; Ieda, Junichi

Journal of Magnetism and Magnetic Materials, 491, p.165550_1 - 165550_5, 2019/12

https://doi.org/10.1016/j.jmmm.2019.165550

Spin-transfer torques in antiferromagnetic textures; Efficiency and quantification method

Yamane, Yuta*; Ieda, Junichi; Sinova, J.*

Physical Review B, 94(5), p.054409_1 - 054409_8, 2016/08

AA2016-0164.pdf:0.5MB

https://doi.org/10.1103/PhysRevB.94.054409

We formulate a theory of spin-transfer torques in antiferromagnets, which covers the small to large limits of the exchange coupling energy relative to the kinetic energy of the inter-sublattice electron dynamics. Our theory suggests a natural definition of the efficiency of spin-transfer torques in antiferromagnets in terms of well-defined material parameters, revealing that the charge current couples predominantly to the antiferromagnetic order parameter and the sublattice-canting moment in, respectively, the limits of large and small exchange coupling. The effects can be quantified by analyzing the antiferromagnetic spin-wave dispersions in the presence of charge current: in the limit of large exchange coupling the spin-wave Doppler shift always occurs, whereas, in the opposite limit, the only spin-wave modes to react to the charge current are ones that carry a pronounced sublattice-canting moment. The findings offer a framework for understanding and designing spin-transfer torques in antiferromagnets belonging to different classes of sublattice structures such as, e.g., bipartite and layered antiferromagnets.

Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient

Yamane, Yuta*; Hemmatiyan, S.*; Ieda, Junichi; Maekawa, Sadamichi; Sinova, J.*

Scientific Reports (Internet), 4, p.6901_1 - 6901_5, 2014/11

https://doi.org/10.1038/srep06901

Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient.

Real-time analysis of the spinmotive force due to domain wall motion

Ieda, Junichi; Maekawa, Sadamichi; Yamane, Yuta

Journal of the Korean Physical Society, 62(12), p.1802 - 1806, 2013/06

https://doi.org/10.3938/jkps.62.1802

Spinmotive force, which is induced by motion of a nonuniform magnetic nanostructure, reflects real time dynamics of the magnetization texture. Using numerical simulations we study the spinmotive force associated with domain wall motion and find that its dc component scales with an applied magnetic field even in a field range where the wall motion is no longer associated with periodic angular rotation of the wall magnetization. As the field is increased, spikes in the voltage signals start to appear, which are mainly associated with vortex core nucleation and annihilation. At high fields, the slope of the generated dc voltage with the applied field is expected to be only dependent on the spin polarization of conduction electrons and thus can be used to accurately determine the degree of spin polarization in various materials.

Stability of spinmotive force in perpendicularly magnetized nanowires under high magnetic fields

Yamane, Yuta; Ieda, Junichi; Maekawa, Sadamichi

Applied Physics Letters, 100(16), p.162401_1 - 162401_3, 2012/04

https://doi.org/10.1063/1.4703933

Continuous generation of spinmotive force in a patterned ferromagnetic film

Yamane, Yuta; Sasage, Kohei*; An, Toshu*; Harii, Kazuya*; Oe, Junichiro*; Ieda, Junichi; Barnes, S. E.*; Saito, Eiji; Maekawa, Sadamichi

Physical Review Letters, 107(23), p.236602_1 - 236602_4, 2011/11

https://doi.org/10.1103/PhysRevLett.107.236602

Equation-of-motion approach of spin-motive force

Yamane, Yuta; Ieda, Junichi; Oe, Junichiro*; Barnes, S. E.*; Maekawa, Sadamichi

Journal of Applied Physics, 109(7), p.07C735_1 - 07C735_3, 2011/04

https://doi.org/10.1063/1.3565398