Universality classes of the domain-wall creep motion driven by spin-transfer torques

With the stochastic Landau-Lifshitz-Gilbert equation, we numerically simulate the creep motion of a magnetic domain wall driven by the adiabatic and nonadiabatic spin-transfer torques induced by the electric current. The creep exponent mu and the roughness exponent zeta are accurately determined from the scaling behaviors. The creep motions driven by the adiabatic and nonadiabatic spin-transfer torques belong to different universality classes. The scaling relation between mu and zeta based on certain simplified assumptions is valid for the nonadiabatic spin-transfer torque, while invalid for the adiabatic one. Our results are compatible with the experimental ones, but go beyond the existing theoretical prediction. Our investigation reveals that the disorder-induced pinning effect on the domain-wall rotation alters the universality class of the creep motion.

Automated summary

By numerically simulating the creep motion of a magnetic domain wall driven by electric current, we accurately determined the creep exponent and roughness exponent from scaling behaviors, finding that the adiabatic and nonadiabatic spin-transfer torques belong to different universality classes and exhibit different scaling relations. Our results are in line with experimental data, but surpass existing theoretical predictions, revealing the impact of disorder-induced pinning effect on altering the universality class of creep motion.