Surface-induced cubic anisotropy in nanomagnets

TL;DR

This study explores how surface anisotropy influences the magnetic behavior of nanomagnets, demonstrating that under certain conditions, their complex many-spin dynamics can be effectively modeled by a simplified macrospin with combined anisotropy effects.

Contribution

It shows that surface anisotropy effects in nanomagnets can be accurately represented by an effective macrospin model with uniaxial and cubic anisotropy terms.

Findings

Many-spin particle behavior can be modeled by a macrospin with effective anisotropy.

Effective energy includes uniaxial and cubic anisotropy terms.

Model applies to both transverse and Ne9el's surface anisotropy models.

Abstract

We investigate the effect of surface anisotropy in a spherical many-spin magnetic nanoparticle. By computing minor loops, two-dimensional (2D) and 3D energyscape, and by investigating the behavior of the net magnetization, we show that in the case of not too strong surface anisotropy the behavior of the many-spin particle may be modeled by that of a macrospin with an effective energy containing uniaxial and cubic anisotropy terms. This holds for both the transverse and N\'eel's surface anisotropy models.