Critical dynamics of a uniaxial and dipolar ferromagnet

TL;DR

This paper investigates the critical dynamics of three-dimensional uniaxial dipolar ferromagnets, analyzing how exchange and dipole interactions influence spin correlations and transport, with results aligning with experiments on Gd.

Contribution

It introduces a mode coupling theory analysis of critical dynamics in uniaxial dipolar ferromagnets, identifying the crossover behavior and universality class for Gd.

Findings

Quantitative agreement with hyperfine interaction experiments on Gd.

Identification of the universality class for Gd.

Best fit of μSR relaxation rate assuming muons occupy octahedral sites.

Abstract

We study the critical dynamics of three-dimensional ferromagnets with uniaxial anisotropy by taking into account exchange and dipole-dipole interaction. The dynamic spin correlation functions and the transport coefficients are calculated within a mode coupling theory. It is found that the crossover scenario is determined by the subtle interplay between three length scales: the correlation length, the dipolar and uniaxial wave vector. We compare our theoretical findings with hyperfine interaction experiments on Gd and find quantitative agreement. This analysis allows us to identify the universality class for Gd. It also turns out that the $\mu$SR relaxation rate can be best fitted if it is assumed that muons occupy octahedral interstitials sites within the Gd lattice.