Influence of uniaxial anisotropy on domain wall motion driven by spin torque

Abstract

Magnetization dynamics of a bilayer structure in the presence of a spin-transfer torque is studied using an atomistic model coupled with a model of spin accumulation. The spin-transfer torque is decomposed into two components: adiabatic and nonadiabatic torques, expressed in terms of the spin accumulation, which is introduced into the atomistic model as an additional field. The evolution of the magnetization and the spin accumulation are calculated self-consistently. We introduce a spin-polarized current into a material containing a domain wall whose width is varied by changing the anisotropy constant. It is found that the adiabatic spin torque tends to develop in the direction of the magnetization whereas the nonadiabatic spin torque arising from the mistracking of conduction electrons and local magnetization results in out-of-plane magnetization components. However, the adiabatic spin torque significantly dominates the dynamics of the magnetization. The total spin-transfer torque acting on the magnetization increases with the anisotropy constant due to the increasing magnetization gradient.