Magnetic excitations affected by spin-lattice coupling in the S=32 triangular lattice antiferromagnet Ag2CrO2

Abstract

Ag2CrO2 is an S=32 triangular lattice antiferromagnet in which long-range magnetic order with a fivefold magnetic unit cell appears below the transition temperature (TN) of 24 K. The long-range magnetic order is accompanied by a structural transition. Inelastic neutron scattering experiments were performed to investigate the magnetic interactions, anisotropy, and correlations in this material. Above TN, diffuse scattering originating from the short-ranged magnetic correlations consistent with a 120∘ structure was observed. The magnetic excitations below TN were reproduced reasonably well using a linear spin-wave model with further-neighbor interactions and easy-axis anisotropy, which are predicted to be due to a previously proposed spin-lattice coupling [Wang and Vishwanath, Phys. Rev. Lett. 100, 077201 (2008)].