Magnetic excitations affected by spin-lattice coupling in the S = 3 2 triangular lattice antiferromagnet Ag 2 CrO 2

${\mathrm{Ag}}_{2}{\mathrm{CrO}}_{2}$ is an $S=\frac{3}{2}$ triangular lattice antiferromagnet in which long-range magnetic order with a fivefold magnetic unit cell appears below the transition temperature (${T}_{\mathrm{N}}$) 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 ${T}_{\mathrm{N}}$, diffuse scattering originating from the short-ranged magnetic correlations consistent with a ${120}^{\ensuremath{\circ}}$ structure was observed. The magnetic excitations below ${T}_{\mathrm{N}}$ 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)].