Z₂Vortex-Induced Broadening of the EPR Linewidth in the Two-Dimensional Triangular Lattice Antiferromagnets, HCrO₂and LiCrO₂

Abstract

The title compounds are the family of the AMO 2 -type (R\bar3m) crystal which has a pronounced layer structure and are promising candidates for the two-dimensional Heisenberg triangular lattice antiferromagnet (2DH TAL-AF). The interesting observation is that a singular point of the EPR signal is located around T KM =0.66 J S 2 for the critical temperature of phase transition associated with the pairing-dissociation of the Z 2 vortices, suggesting the present system behaves as 2DH TAL-AF down to very close to T KM . The EPR linewidth exhibits Z 2 vortex-induced broadening above the critical temperature which is inversely proportional to the thermally excited vortex density, n v ∝exp (- E v / k B T ) with the activation energy \(E_{\text{v}}{\cong}4k_{\text{B}}T_{\text{KM}}\).