Effect of Gold Impurities on the Critical Properties ofcuMn Spin-Glasses

We present SQUID measurements of the nonlinear susceptibility ${\chi }_{\mathrm{nl}}$ of "pure" CuMn and CuMn doped with gold impurities with concentrations $C_{\mathrm{Au}}$ of 1, 2, and 3 at.%. Gold impurities suppress the magnitude of ${\chi }_{\mathrm{nl}}$. Ordinary one-parameter scaling with respect to field and temperature is obeyed by ${\chi }_{\mathrm{nl}}$ of the pure CuMn. However, strong deviations from this scaling behavior are observed in the gold-doped samples in the vicinity of the freezing temperature and in low fields, $H<\mathrm{}{H}^{*}$ where $H^{*}$ increases with $c$. This is interpreted as the onset of an anisotropy-induced crossover from a Heisenberg to an Ising spin-glass critical behavior.