Macroscopic Anisotropy and Symmetry Breaking in the Pyrochlore Antiferromagnet Gd$_{2}$Ti$_{2}$O$_{7}$}

TL;DR

This study investigates the temperature-dependent anisotropy and symmetry breaking in the pyrochlore antiferromagnet Gd2Ti2O7 using ESR, revealing anisotropy emerging below 80 K due to superexchange interactions and short-range correlations.

Contribution

It demonstrates that anisotropy and symmetry breaking can arise from superexchange interactions and short-range correlations in a geometrically frustrated antiferromagnet.

Findings

Anisotropy appears below 80 K with respect to [111] direction.

Two ESR modes are explained by short-range planar correlations.

Anisotropy is driven by superexchange interactions despite Gd3+ being spin-only.

Abstract

In the Heisenberg antiferromagnet $Gd_2Ti_2O_7$, the exchange interactions are geometrically frustrated by the pyrochlore lattice structure. This ESR study reveals a strong temperature dependent anisotropy with respect to a [111] body diagonal below a temperature $T_A=80$ K, despite the spin only nature of the $Gd^{3+}$ ion. Anisotropy and symmetry breaking can nevertheless appear through the superexchange interaction. The presence of short range planar correlation restricted to specific Kagom\'{e} planes is sufficient to explain the two ESR modes studied in this work.