Magnetic properties of dense nanoparticle arrays with core/shell morphology

TL;DR

This study models the magnetic hysteresis of dense, ordered nanoparticle arrays with core/shell structures, revealing how dipolar interactions and packing density influence coercivity and exchange bias.

Contribution

It introduces a computational approach to analyze the magnetic behavior of core/shell nanoparticle arrays considering dipolar and exchange interactions.

Findings

Coercivity decreases with stronger dipolar coupling.

Exchange bias field exhibits non-monotonous behavior due to competing interactions.

Increasing packing density can enhance the exchange bias field.

Abstract

We calculate the magnetization hysteresis for an ordered array of composite magnetic nanoparticles with a ferromagnetic (FM) core and an antiferromagnetic (AFM) shell, located on a triangular lattice and coupled via magnetostatic forces. Each nanoparticle is described by a pair of exchange-coupled (J), anisotropic spins (Meiklejohn-Bean model). The magnetization hysteresis loop is obtained using the Metropolis Monte Carlo algorithm. For magnetically hard nanoparticles we find that the coercivity is reduced with increasing the dipolar coupling strength, while the exchange bias field shows an non-monotonous behavior resulting from the competition between the random anisotropy and interparticle dipolar interactions. The possibility of enhancing the exchange bias field by increasing the packing density is discussed.