Current-Induced Resonant Motion of a Magnetic Vortex Core: Effect of Nonadiabatic Spin Torque

TL;DR

This paper investigates how current-induced resonant motion of magnetic vortex cores is affected by nonadiabatic spin torque, highlighting the importance of initial core tilting and proposing experimental methods to measure nonadiabatic effects.

Contribution

It provides analytical and micromagnetic insights into vortex core dynamics, emphasizing the role of nonadiabatic spin torque and initial tilting angle, which were previously not well understood.

Findings

Resonant motion radius and phase shift are affected by vortex core distortion.

Initial tilting angle is determined by nonadiabatic spin torque and unaffected by Oersted fields.

Time-resolved imaging is crucial for estimating nonadiabaticity experimentally.

Abstract

The current-induced resonant excitation of a magnetic vortex core is investigated by means of analytical and micromagnetic calculations. We find that the radius and the phase shift of the resonant motion are not correctly described by the analytical equations because of the dynamic distortion of a vortex core. In contrast, the initial tilting angle of a vortex core is free from the distortion and determined by the nonadiabaticity of the spin torque. It is insensitive to experimentally uncontrollable current-induced in-plane Oersted field. We propose that a time-resolved imaging of the very initial trajectory of a core is essential to experimentally estimate the nonadiabaticity.