First-principles calculation of 3m spin-orbit torque and its effect on magnetization dynamics

Symmetry-dependent field-free switching of the perpendicular magnetization has been observed in an epitaxial L11-ordered CuPt/CoPt bilayer [1]. The switching is enabled by 3m spin-orbit torque (SOT) arising from the low-symmetry point group (3m1) at the CuPt/CoPt interface. Using a first-principles nonequilibrium Green’s function formalism combined with the Andersen disorder model, we calculate the damping-like (DL), fieldlike (FL), and 3m SOTs in such bilayer by expanding the SOT in the basis of vector spherical harmonics [2,3]. We find that the magnitude of 3m torque is appreciable compared to the DL SOT. We also study the magnetization dynamics using micromagnetics simulations in a perpendicularly magnetized circular nanodisk in the presence of 3m SOT and Dzyaloshinskii-Moriya interaction. We find that the 3m SOT can drive the domain wall motion, and if large enough, can enable the field-free switching of perpendicular magnetization.

Reference:

1. Liu, L., Zhou, C., Shu, X. et al. Nat. Nanotechnol. 16, 277–282 (2021).

2. K. D. Belashchenko, Alexey A. Kovalev, and M. van Schilfgaarde, Phys. Rev. Materials 3, 011401(R) (2019)

3. K. D. Belashchenko, Alexey A. Kovalev, and M. van Schilfgaarde, Phys. Rev. B 101, 020407(R) (2020)