Exchange bias and asymmetric hysteresis loops from a microscopic model of core/shell nanoparticles

TL;DR

This paper uses Monte Carlo simulations to explore how microscopic interactions at the core/shell interface of magnetic nanoparticles cause exchange bias and asymmetric hysteresis loops, providing insights into their microscopic origins.

Contribution

It introduces a microscopic model and simulation approach to explain the origin of exchange bias and asymmetry in hysteresis loops of core/shell nanoparticles.

Findings

Hysteresis loop shifts increase with interfacial exchange coupling.

Displacements along the magnetization axis grow with stronger coupling.

Overlap functions reveal microscopic origins of observed features.

Abstract

We present Monte Carlo simulations of hysteresis loops of a model of a magnetic nanoparticle with a ferromagnetic core and an antiferromegnetic shell with varying values of the core/shell interface exchange coupling which aim to clarify the microscopic origin of exchange bias observed experimentally. We have found loops shifts in the field direction as well as displacements along the magnetization axis that increase in magnitude when increasing the interfacial exchange coupling. Ovelap functions computed from the spin configurations along the loops have been computed to explain the origin and magnitude of these features microscopically.