Gd pyrochlore under a staggered molecular field in Gd$_2$Ir$_2$O$_7$

TL;DR

This study investigates how a staggered molecular field from iridium ions influences the magnetic ground states of Gd$_2$Ir$_2$O$_7$, revealing complex antiferromagnetic arrangements and the role of anisotropic Gd-Gd interactions.

Contribution

It demonstrates the impact of iridium-induced molecular fields on Gd pyrochlore, highlighting the emergence of multiple antiferromagnetic states and the importance of anisotropic Gd-Gd interactions.

Findings

Identification of high-temperature all-in-all-out order induced by Ir field

Detection of Palmer and Chalker correlations at lower temperatures

Evidence of weak easy-plane anisotropy in Gd$^{3+}$ moments

Abstract

The influence of a staggered molecular field in frustrated rare-earth pyrochlores, produced via the magnetic iridium occupying the transition metal site, can generate exotic ground states, such as the fragmentation of the magnetization in the Ho compound. At variance with the Ising Ho$^{3+}$ moment, we focus on the behavior of the quasi isotropic magnetic moment of the Gd$^{3+}$ ion at the rare-earth site. By means of macroscopic measurements and neutron scattering, we find a complex situation where different components of the magnetic moment contribute to two antiferromagnetic non-collinear arrangements: a high temperature all in - all out order induced by the Ir molecular field, and Palmer and Chalker correlations that tend to order at much lower temperatures. This is enabled by the anisotropic nature of the Gd-Gd interactions and requires a weak easy-plane anisotropy of the Gd$^{3+}$ moment due to the mixing of the ground state with multiplets of higher spectral terms.