EPR and FMR study of (C6H5NH3)2CuCl4: Evidence for two-dimensional spin diffusion

Abstract
Bis(anilinium) copper tetrachloride, (C6H5NH3)2CuCl4, is a layered perovskite with ferromagnetic intralayer interactions. At high temperature (T≳200 K), the ESR linewidths ΔH are virtually isotropic and increase linearly with temperature. Extrapolation yields ΔH(ϑ, T = 0) = 3.5(3 cos2 ϑ−1)2. The linewidths are assumed to be given by a contribution ΔHsd(ϑ,∞)2, the spin diffusion enhanced linewidth due to anisotropic exchange only, and ΔH(ϑ,T), the linewidth contribution due to the phonon modulation of the exchange anisotropies. The FMR modes were studied in the ab plane at 4.2 K, as well as the temperature dependence of resonance fields for H‖‖a and H‖‖b. Magnetostatic mode excitations, observed in conjunction with the FMR line were found for temperatures below 11 K.