Spin-orbit Spin-transfer Torque Research Articles

Magnetic domain wall motion across a step of Dzyaloshinskii-Moriya interaction

Magnetic domain wall motion is numerically studied in a nanowire with a Dzyaloshinskii-Moriya interaction (DMI) step at which DMI varies in real space. The spatially modulated DMI results in the formation of asymmetric domain wall energy landscape across the step, which affects the domain wall motion significantly. Utilizing this DMI step, we propose a domain wall memory device where the switching of up- and down-state is induced by a spin-orbit spin-transfer torque (SOT)-driven domain wall motion. This domain wall memory device is expected to have a high switching efficiency.

Magnetization dynamics driven by angle-dependent spin-orbit spin-transfer torque

Spin-orbit spin transfer torque allows an efficient control of magnetization by an in-plane current. Recent experiments found that the spin-orbit torque has strong dependence on the magnetization angle [Garello et al., Nature Nanotechnol. 8, 587 (2013); Qiu et al., Sci. Rep. 4, 4491 (2014)]. We theoretically investigate magnetization switching and domain wall motion in a perpendicularly magnetized layer, induced by angle-dependent spin-orbit torque. We obtain analytic expressions of the switching current and domain wall velocity, in agreement with numerical results. Based on the expressions, we find that the spin-orbit torque increasing with the polar angle of magnetization is beneficial for both switching and domain wall motion. Our result will serve as a guideline to design and interpret switching and domain wall experiments based on spin-orbit torque.