Equilibrium spin-glass transition of magnetic dipoles with random anisotropy axes

TL;DR

This study provides numerical evidence for an equilibrium spin glass phase in three-dimensional magnetic dipole systems with random axes, characterized by a specific transition temperature, order parameter behavior, and diverging correlation length.

Contribution

It demonstrates the existence of a spin glass transition in dipolar systems with random anisotropy axes using Monte Carlo simulations, detailing critical properties and phase behavior.

Findings

Spin glass phase exists below T_c in 3D systems.

Overlap parameter follows a square root temperature dependence.

Correlation length diverges at T_c with critical exponent ν=1.5±0.5.

Abstract

We study fully occupied lattice systems of classical magnetic dipoles which point along random axes. Only dipolar interactions are considered. From tempered Monte Carlo simulations, we obtain numerical evidence that supports the following conclusions: in three dimensions, (a) there is an equilibrium spin glass phase at temperatures below $T_c$, where $k_BT_c= (0.86\pm 0.07)\varepsilon_d $ and $\varepsilon_d$ is a nearest neighbor dipole-dipole interaction energy, (b) in the spin glass phase the overlap parameter is approximately given by $\sqrt{1-T/T_c}$, and (c) the correlation length $\xi$ diverges at $T_c$ with a critical exponent $\nu =1.5\pm0.5$; in two dimensions $\xi$ diverges at or near T=0 and $\nu=3\pm1$.