Monte Carlo Study of Maghemite Nanoparticles

TL;DR

This study uses Monte Carlo simulations to analyze the magnetic properties of maghemite nanoparticles, focusing on the effects of surface anisotropy on their thermal and magnetic behavior.

Contribution

It introduces a simple model of maghemite nanoparticles with core and surface spins, exploring how surface anisotropy influences magnetic properties.

Findings

Surface anisotropy affects blocking temperature.

Surface anisotropy influences coercive fields.

Magnetic hysteresis behavior depends on nanoparticle size.

Abstract

We consider a simple model of maghemite nanoparticles and study their magnetic properties using Monte Carlo methods. The particles have a spherical geometry with diameters ranging from 3 nm to 8 nm. The interior of the particles consists of core spins with exchange interactions and anisotropy given by the values in the bulk material. The outer layer of the particles consists of surface spins with weaker exchange interactions but an enhanced anisotropy. The thermal behaviour of the total, core and surface magnetizations are calculated as well as the hysteresis loops due to the application of an applied field. The effect of the surface anisotropy on the blocking temperature, the coercive and exchange bias fields is studied.