0000000000387864
AUTHOR
Kei Yamamoto
showing 6 related works from this author
Tunable Sign Change of Spin Hall Magnetoresistance in Pt/NiO/YIG Structures
2017
Spin Hall magnetoresistance (SMR) has been investigated in Pt/NiO/YIG structures in a wide range of temperature and NiO thickness. The SMR shows a negative sign below a temperature that increases with the NiO thickness. This is contrary to a conventional SMR theory picture applied to the Pt/YIG bilayer, which always predicts a positive SMR. The negative SMR is found to persist even when NiO blocks the spin transmission between Pt and YIG, indicating it is governed by the spin current response of the NiO layer. We explain the negative SMR by the NiO "spin flop" coupled with YIG, which can be overridden at higher temperature by positive SMR contribution from YIG. This highlights the role of m…
Spin caloric effects in antiferromagnets assisted by an external spin current
2018
Searching for novel spin caloric effects in antiferromagnets we study the properties of thermally activated magnons in the presence of an external spin current and temperature gradient. We predict the spin Peltier effect -- generation of a heat flux by spin accumulation -- in an antiferromagnetic insulator with cubic or uniaxial magnetic symmetry. This effect is related with spin-current induced splitting of the relaxation times of the magnons with opposite spin direction. We show that the Peltier effect can trigger antiferromagnetic domain wall motion with a force whose value grows with the temperature of a sample. At a temperature, larger than the energy of the low-frequency magnons, this…
Anatomy of spin–orbit torques
2017
The use of time-resolved X-ray microscopy allows a direct visualization of the magnetization switching for nanomagnets under the effect of spin–orbit torques.
古典波動現象のトポロジーによる特徴付け; 静磁スピン波表面モードのトポロジカルな起源
2019
We propose a topological characterization of Hamiltonians describing classical waves. Applying it to the magnetostatic surface spin waves that are important in spintronics applications, we settle the speculation over their topological origin. For a class of classical systems that includes spin waves driven by dipole-dipole interactions, we show that the topology is characterized by vortex lines in the Brillouin zone in such a way that the symplectic structure of Hamiltonian mechanics plays an essential role. We define winding numbers around these vortex lines and identify them to be the bulk topological invariants for a class of semimetals. Exploiting the bulk-edge correspondence appropriat…
Anomalous Hall effect driven by dipolar spin waves in uniform ferromagnets
2015
A new type of anomalous Hall effect is shown to arise from the interaction of conduction electrons with dipolar spin waves in ferromagnets. This effect exists even in homogeneous ferromagnets without relativistic spin-orbit coupling. The leading contribution to the Hall conductivity is proportional to the chiral spin correlation of dynamical spin textures and is physically understood in terms of the skew scattering by dipolar magnons.
Spin transfer torques and spin-dependent transport in a metallic F/AF/N tunneling junction
2018
We study spin-dependent electron transport through a ferromagnetic-antiferromagnetic-normal metal tunneling junction subject to a voltage or temperature bias, in the absence of spin-orbit coupling. We derive microscopic formulas for various types of spin torque acting on the antiferromagnet as well as for charge and spin currents flowing through the junction. The obtained results are applicable in the limit of slow magnetization dynamics. We identify a parameter regime in which an unconventional damping-like torque can become comparable in magnitude to the equivalent of the conventional Slonczewski's torque generalized to antiferromagnets. Moreover, we show that the antiferromagnetic sublat…