Anisotropy and field dependence of the electron-paramagnetic-resonance linewidth ofAg: Dy

Here we report measurements of the EPR linewidths for the ${\Gamma }_7$ ground state of $\mathrm{Ag}$ Dy at 9 and 35 GHz and 1.45 K. Our data show linewidth anisotropies that depend on the magnetic field. To analyze the experimental data, two models are discussed. In the first, we consider modifications of the Korringa relaxation due to the Zeeman interaction; in the second, the effect on the linewidth of random stresses in the sample using a model that preserves the full cubic local symmetry at the impurity sites. The second model is able to account for the experimental data and allows us to obtain information about the stress distribution in the sample.