Enhancement of magnetic anisotropy barrier in long range interacting spin systems

TL;DR

This paper provides a unified theoretical description of magnetization decay in anisotropic spin systems, revealing that long-range interactions significantly enhance the magnetic anisotropy energy barrier, especially compared to short-range systems.

Contribution

It introduces a unified model for magnetization decay considering both coherent rotation and nucleation, highlighting how long-range interactions increase the anisotropy energy barrier beyond traditional short-range limits.

Findings

Anisotropy energy barrier scales with particle volume for on-site anisotropy.

For exchange anisotropy, the barrier scales faster than volume, proportional to V^{2-rac{ ext{alpha}}{d}}.

Long-range interactions substantially enhance magnetic stability compared to short-range interactions.

Abstract

Magnetic materials are usually characterized by anisotropy energy barriers which dictate the time scale of the magnetization decay and consequently the magnetic stability of the sample. Here we present a unified description, which includes coherent rotation and nucleation, for the magnetization decay in generic anisotropic spin systems. In particular, we show that, in presence of long range exchange interaction, the anisotropy energy barrier grows as the volume of the particle for on site anisotropy, while it grows even faster than the volume for exchange anisotropy, with an anisotropy energy barrier proportional to $V^{2-\alpha/d}$, where $V$ is the particle volume, $\alpha \leq d $ is the range of interaction and $d$ is the embedding dimension. These results shows a relevant enhancement of the anisotropy energy barrier w.r.t. the short range case, where the anisotropy energy barrier grows as the particle cross sectional area for large particle size or large particle aspect ratio.