Magnetic relaxation phenomena in Dy-Sc alloys

Neutron-scattering and magnetization experiments on ${R}_{x}{\mathrm{Sc}}_{1\ensuremath{-}x}$ ($R=\mathrm{G}\mathrm{d},\phantom{\rule{0ex}{0ex}}\mathrm{T}\mathrm{b},\phantom{\rule{0ex}{0ex}}\mathrm{H}\mathrm{o},\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{n}\mathrm{d}\phantom{\rule{0ex}{0ex}}\mathrm{E}\mathrm{r}$) alloys have given anomalous results for the concentration dependence of the magnetic-ordering temperature. In contrast to conventional theoretical arguments and to data on other rare-earth alloys, these systems require large rare-earth concentrations ($15%l~xl~39%$) for the onset of long-range magnetic order to occur. The work which we report here deals with the investigation of the ${\mathrm{Dy}}_{x}{\mathrm{Sc}}_{1\ensuremath{-}x}$ system in the concentration range $0.02l~xl~0.75$. The M\"ossbauer effect was used to examine the magnetic hyperfine interaction at the $^{161}\mathrm{Dy}$ nuclei both as a function of temperature and concentration. Neutron scattering on the samples containing 35-at.% Dy indicated no long-range magnetic order at $T=4.2$ K. However, each of the alloys investigated, including the 2-at.% Dy alloy which was the lowest concentration measured, exhibits a well-defined magnetic hyperfine splitting at this temperature. The magnitude of this splitting is 45 \ifmmode\pm\else\textpm\fi{} 0.5 cm/sec and corresponds to a field approximately equal to that found in pure Dy metal, and is independent of the Dy concentration contained in the alloy. The observed magnetic hyperfine lines for the alloys in the lower Dy concentration region (\ensuremath{\le}25%) are relaxation broadened with increasing temperature, while the overall splitting remains essentially independent of temperature. These spectra are analyzed in terms of an electronic-spin-relaxation model for an effective spin-\textonehalf{} system.