Current-induced instability of domain walls in cylindrical nanowires

TL;DR

This study investigates how current-induced effects influence domain wall motion in cylindrical nanowires, revealing that spin wave emission limits their maximum velocity and affects stability, especially in multiple domain wall systems.

Contribution

It demonstrates the impact of nonlocal spin-transfer torque on domain wall stability and velocity limits, highlighting differences from local torque models in cylindrical nanowires.

Findings

Spin waves are generated with nonlocal torque but not with local torque.

Transverse domain walls have an upper velocity limit due to wave packet instability.

Nonlocal torque results in a smaller stable velocity region compared to local torque.

Abstract

We study the current-driven domain wall (DW) motion in cylindrical nanowires using micromagnetic simulations by implementing the Landau-Lifshitz-Gilbert equation with nonlocal spin-transfer torque in a finite difference micromagnetic package. We find that in the presence of DW Gaussian wave packets (spin waves) will be generated when the charge current is applied to the system suddenly. And this effect is excluded when using the local spin-transfer torque. The existence of spin waves emission indicates that transverse domain walls can not move arbitrarily fast in cylindrical nanowires although they are free from the Walker limit. We establish an upper-velocity limit for the DW motion by analyzing the stability of Gaussian wave packets using the local spin-transfer torque. Micromagnetic simulations show that the stable region obtained by using nonlocal spin-transfer torque is smaller than that by using its local counterpart. This limitation is essential for multiple domain walls since the instability of Gaussian wave packets will break the structure of multiple domain walls.