Thermal stability of coupled ferromagnetic and superparamagnetic particles

TL;DR

This paper investigates how thermal fluctuations influence the magnetization reversal in a coupled system of ferromagnetic and superparamagnetic particles, revealing effects of coupling on effective anisotropy and external field.

Contribution

It introduces a model for thermally activated magnetization dynamics in coupled particles, accounting for the impact of coupling sign on anisotropy and external magnetic field modifications.

Findings

Coupling alters the effective anisotropy field of the ferromagnetic particle.

The external magnetic field experienced by the particle is modified depending on coupling sign.

The model simplifies the complex reversal process to a single-particle dynamics with adjusted parameters.

Abstract

We consider a single-domain ferromagnetic particle with uniaxial anisotropy coupled to a single-domain soft ferromagnetic particle (superparamagnetic particle). The problem of thermally agitated magnetization reversal in this case can be reduced to the random magnetization dynamics of the first particle with an effectively larger anisotropy field. The magnetic external field is also altered in a manner that depends on the sign of the coupling and can be either enhanced or suppressed.