Role of atomic vacancies and second-neighbor antiferromagnetic-exchange coupling in a ferromagnetic nanoparticle

TL;DR

This study uses Monte-Carlo simulations to explore how atomic vacancies and second-neighbor antiferromagnetic exchange influence the magnetic behavior of ferromagnetic nanoparticles, revealing factors that enhance superparamagnetism.

Contribution

It introduces a detailed simulation approach to analyze the combined effects of atomic vacancies and long-range exchange interactions on nanoparticle magnetism.

Findings

Atomic vacancies and second-neighbor antiferromagnetic exchange enhance superparamagnetic behavior.

Broken bonds due to vacancies significantly affect magnetic properties.

Long-range exchange coupling influences temperature-dependent magnetization.

Abstract

Several factors may be responsible for disorder and frustration in a magnetic nanoparticle, including atomic vacancies on the surface and inside, impurity atoms, long-range magnetic exchange coupling, etc. We use Monte-Carlo simulations within the Heisenberg model to examine the role of randomly distributed atomic vacancies and long-range magnetic-exchange coupling on the temperature-dependent magnetic properties of ferromagnetic nanoparticles. In particular, we study the role of the second-neighbor antiferromagnetic exchange coupling and missing atoms inside the particle resulting in broken nearby bonds. We find that both factors may enhance the superparamagnetic behaviors of such particles.