Vortex dynamics and frustration in two-dimensional triangular chromium lattices

Abstract

The spin dynamics of the two-dimensional (2D) triangular lattice antiferromagnets ${\text{HCrO}}_{2}$, ${\text{LiCrO}}_{2}$, and ${\text{NaCrO}}_{2}$ is investigated by electron spin resonance. In these oxides, on approaching the N\'eel temperature ${T}_{\text{N}}$ from above, the divergence of the temperature dependent linewidth is well described in terms of a Berezinskii-Kosterlitz-Thouless scenario due to magnetic vortex-antivortex pairing. A refined analysis suggests analogies to the melting scenario of a 2D triangular lattice described by Nelson, Halperin, and Young.