Temperature dependence of hyperfine interactions in Dy-Gd alloys

The magnetic hyperfine field and quadrupole interaction have been measured in pure dysprosium and three gadolinium-dysprosium alloys using the Mössbauer effect on the dysprosium nucleus. The temperature dependences of $H_{\mathrm{hf}}$ and $V_{\mathrm{zz}}$ were determined from 4 K up to the ordering temperatures and compared to theory. The hyperfine field obeyed a conventional spin-wave analysis with an anisotropy gap of order 20 K. The quadrupole interaction was found to have the same temperature dependence as predicted theoretically for the single-ion anisotropy. No systematic variation in the low temperature values of $H_{\mathrm{hf}}$ or $V_{\mathrm{zz}}$ was observed with concentration.