Influence of surface anisotropy on the magnetization reversal of nanoparticles

TL;DR

This study uses Monte Carlo simulations to examine how surface anisotropy influences magnetization reversal in ellipsoidal maghemite nanoparticles, revealing the formation of hedgehog-like spin structures and mode changes with surface anisotropy and particle shape.

Contribution

It introduces a detailed analysis of surface anisotropy effects on nanoparticle magnetization reversal using Monte Carlo methods, highlighting new spin structures and reversal modes.

Findings

Radial surface anisotropy promotes hedgehog-like spin structures.

Increasing surface anisotropy or elongation changes the reversal mode.

Hysteresis loops vary with particle shape and surface anisotropy.

Abstract

The influence of surface anisotropy on the magnetization processes of maghemite nanoparticles with ellipsoidal shape is studied by means of Monte Carlo simulations. Radial surface anisotropy is found to favor the formation of hedgehog-like spin structures that become more stable as the surface anisotropy constant at the surface $k_S$ is increased form the value at the core. We have studied the change in the low temperature hysteresis loops with the particle aspect ratio and with $k_S$, finding a change in the magnetization reversal mode as $k_S$ or the particle elongation is increased.