Magnetic Reversal in Nanoscopic Ferromagnetic Rings

TL;DR

This paper develops a theoretical model for magnetization reversal in nanoscopic ferromagnetic rings, highlighting their enhanced stability and predicting a phase transition between different activation regimes influenced by magnetic field variations.

Contribution

It introduces a novel theory accounting for thermal fluctuations and nonlocal magnetostatic effects in magnetic rings, predicting a phase transition in reversal behavior.

Findings

Magnetic rings exhibit greater stability against reversal than other geometries.

A phase transition between Arrhenius and non-Arrhenius regimes is predicted.

The effects of nonlocal magnetostatic forces are quantitatively evaluated.

Abstract

We present a theory of magnetization reversal due to thermal fluctuations in thin submicron-scale rings composed of soft magnetic materials. The magnetization in such geometries is more stable against reversal than that in thin needles and other geometries, where sharp ends or edges can initiate nucleation of a reversed state. The 2D ring geometry also allows us to evaluate the effects of nonlocal magnetostatic forces. We find a `phase transition', which should be experimentally observable, between an Arrhenius and a non-Arrhenius activation regime as magnetic field is varied in a ring of fixed size.