Theoretical study of spin torque and domain wall motion on ferromagnetic Kagome lattice

We theoretically study spin torque and domain wall motion induced electrically in a ferromagnetic Kagome lattice, which has spin-orbit coupling. For details, we suppose the exchange interaction with an inhomogeneous magnetic texture of uniaxial magnetic anisotropy and the spin-dependent second-nearest neighbor hopping acting as the spin-orbit coupling. Because of the chiral edge conduction, electric charges are accumulated around the domain wall. We calculate the spin polarization of localized charges as a response of the electric field by the Kubo formula. As a result, the spins of localized charges are polarized and exert spin torque on the domain wall.
Firstly, we discuss the spin torque and domain wall motion in two-dimensional limits of the ferromagnetic Kagome lattice. [1] Second, we extend the 2D model to thin films of Kagome-lattice shandite, [2] which are more realistic. All of the two models cause non-adiabatic spin-transfer torque on the domain wall reducing the intrinsic threshold current. These results and discussions suggest a good comparison between ideal models and realistic models in terms of spin torques in topological materials.

[1] S. Kim, D. Kurebayashi and K. Nomura, J. Phys. Soc. Jpn. 88, 083704 (2019).
[2] A. Ozawa and K. Nomura, arXiv :1904.08148