Monte Carlo simulation of the equilibrium spin glass phase in disordered assemblies of magnetic nanoparticles

Abstract

This chapter is about the collective effects that are brought about by dipole‐dipole interactions in disordered assemblies of magnetic nanoparticles (NP). We focus on NPs which have single magnetic domains and large uniaxial anisotropics. We first discuss time dependent properties of these systems, such as the zero field cooled (ZFC) and field cooled (FC) magnetic susceptibility and aging, and report some results we obtain making use of the Metropolis Monte Carlo algorithm. For equilibrium behavior, we turn to the parallel tempered Monte Carlo method. A brief introduction to the method is followed by equilibrium results we have recently obtained, mainly, systems of magnetic dipoles with random anisotropy axes have, (a) below some non‐zero temperature Tc, a thermodynamic spin glass phase in three dimensions, but (b) in one layer assemblies, a spin glass phase only at or near zero temperature.This chapter is about the collective effects that are brought about by dipole‐dipole interactions in disordered assemblies of magnetic nanoparticles (NP). We focus on NPs which have single magnetic domains and large uniaxial anisotropics. We first discuss time dependent properties of these systems, such as the zero field cooled (ZFC) and field cooled (FC) magnetic susceptibility and aging, and report some results we obtain making use of the Metropolis Monte Carlo algorithm. For equilibrium behavior, we turn to the parallel tempered Monte Carlo method. A brief introduction to the method is followed by equilibrium results we have recently obtained, mainly, systems of magnetic dipoles with random anisotropy axes have, (a) below some non‐zero temperature Tc, a thermodynamic spin glass phase in three dimensions, but (b) in one layer assemblies, a spin glass phase only at or near zero temperature.