Off-centered immobile magnetic vortex under influence of spin-transfer torque

TL;DR

This paper investigates how spin-transfer torque influences the equilibrium magnetization distribution in magnetic nanoparticles, revealing shape-dependent vortex configurations and the formation of dip structures under current influence.

Contribution

It introduces the concept of off-centered vortices in different nanoparticle shapes caused by spin-transfer torque and analyzes their dependence on current and geometry.

Findings

Off-centered out-of-plane vortex in disk-shaped particles.

Pure planar vortex in asymmetric ring-shaped particles.

Dip structures depend on current strength and displacement, not vortex polarity.

Abstract

Equilibrium magnetization distribution of the vortex state magnetic nanoparticle is affected by the influence of the spin-transfer torque: an off-center out--of--plane vortex appears in the case of the disk shape particle and pure planar vortex in the case of asymmetric ring shape particle. The spin current causes extra out-of-plane magnetization structures identical to well known dip structures for the moving vortex. The shape of the dip structure depends on the current strength and value of the off-center displacement and it does not depend on the vortex polarity. The critical current depends on the nanodot thickness.