Specific Heat of Insulating Spin-Glasses, (Eu,Sr)S, near the Onset of Ferromagnetism

Abstract

The specific heat, $C\left(T\right)\mathrm{}$, of the insulating spin-glass ${\mathrm{Eu}}_x{\mathrm{Sr}}_{1-x}\mathrm{S}$ with $x=0.40\mathrm{}$ exhibits a linear term $\gamma T$ and no singularity at $T_f$, like metallic spin-glasses. A new term, $\delta T^{-2\mathrm{}}$, is found which may arise from totally decoupled clusters created by frustration. The field dependence, $\gamma \mathrm{}\left(B\right)\mathrm{}$ and $\delta \mathrm{}\left(B\right)\mathrm{}$, show maxima. With $x=0.54\mathrm{}$ the behavior is similar. $C(T, B)$ and $\chi (T, B)$ there indicate the spin-glass phase to be supressed at $B=1\mathrm{}$ T.