Spin Hamiltonian, Competing Small Energy Scales and Incommensurate Long Range Order in the Highly Frustrated Gd3Ga5O12 Garnet Antiferromagnet

TL;DR

This study uses mean-field theory to analyze the highly frustrated Gd3Ga5O12 garnet, revealing the importance of long-range dipolar interactions in explaining its incommensurate magnetic order and low-temperature properties.

Contribution

The paper provides the first detailed theoretical explanation of GGG's incommensurate order, emphasizing the role of long-range dipolar interactions in a classical spin Hamiltonian.

Findings

Reproduces spin liquid-like correlations in GGG

Explains sharp peaks in neutron diffraction data

Shows incommensurate order is intrinsic and classical

Abstract

Despite the availability of a spin Hamiltonian for the Gd3Ga5O12 garnet (GGG) for over twenty five years, there has so far been little theoretical insight regarding the many unusual low temperature properties of GGG. Here we investigate GGG in zero magnetic field using mean-field theory. We reproduce the spin liquid-like correlations and, most importantly, explain the positions of the sharp peaks seen in powder neutron diffraction experiments. We show that it is crucial to treat accurately the long-range nature of the magnetic dipolar interactions to allow for a determination of the small exchange energy scales involved in the selection of the experimental ordering wave vector. Our results show that the incommensurate order in GGG is classical in nature, intrinsic to the microscopic spin Hamiltonian and not caused by weak disorder.