Magnetization reversal via internal spin waves in magnetic nanoparticles

TL;DR

This paper demonstrates through numerical simulations that internal spin waves can induce complete magnetization reversal in magnetic nanoparticles, revealing two main instability scenarios and their relaxation dynamics.

Contribution

It introduces a detailed numerical analysis of spin-wave induced magnetization reversal, identifying exponential and linear instability mechanisms and deriving relaxation rates analytically.

Findings

Internal spin waves cause full magnetization reversal in nanoparticles.

Two main instability scenarios: exponential and linear.

Relaxation rates depend on particle orientation, leading to nonexponential relaxation.

Abstract

By numerically solving the equations of motion for atomic spins we show that internal spin-wave processes in large enough magnetic particles, initially in unstable states, lead to complete magnetization reversal and thermalization. The particle's magnetization strongly decreases in the middle of reversal and then recovers. We identify two main scenarios, exponential and linear spin-wave instabilities. For the latter, the longitudinal and transverse relaxation rates have been obtained analytically. Orientation dependence of these rates leads to a nonexponential relaxation of the particle's magnetization at long times.