Low-Temperature Heat Capacity ofβ−Ceriumandβ−Cerium−YttriumAlloys

Abstract

The low-temperature heat capacity of a nearly pure $\beta -\mathrm{Cerium}$ sample ($91\%\beta -9\%\alpha$) and six $\beta$-stabilized Ce-Y alloys were determined between 2.5 and 20 °K. Three principal results were obtained. (i) All six alloys showed magnetic ordering characteristic of $\beta -\mathrm{Cerium}$; the ordering temperatures decreased linearly with yttrium concentration. (ii) The magnetic contribution to the heat capacity of $\beta -\mathrm{Cerium}$ was found to depend on the cube of the temperature in agreement with spin-wave theory for an antiferromagnetic material. (iii) The entropy associated with magnetic ordering ws found to be $R\ln 2$, and is consistent with a crystal field splitting of the $J=\frac{5}{2}$ multiplet into three doublets by the hexagonal lattice.