Frustrated magnetism in the diamond-chain like compound Ba$_{3}$Cu$_{3}$Sc$_{4}$O$_{12}$*

The structure of Ba$_{3}$Cu$_{3}$Sc$_{4}$O$_{12}$, having chains of corner-shared square plaquettes, is reminiscent of the ``diamond chain'' compound Cu$_{3}$(CO$_{3})_{2}$(OH)$_{2}$ which has shown novel magnetic properties. We report preparation of polycrystalline samples of Ba$_{3}$Cu$_{3}$Sc$_{4}$O$_{12}$ followed by temperature dependent magnetic susceptibility \textit{$\chi $(T)} and heat capacity $C_{p}(T)$ measurements in applied magnetic fields up to $H$ = 90 kOe. At high-$T$, \textit{$\chi $(T)} is fitted by the Curie-Weiss law (\textit{$\chi $(T)=C/(T-}$\theta _{CW}))$ and is suggestive of ferromagnetic interactions ($\theta _{CW}$ $\sim $ 70 K). However, in low-fields, the \textit{$\chi $(T)} shows a sharp peak at $T_{N}$ $\sim $ 16 K and the variation at lower temperatures is indicative of antiferromagnetic ordering. Clear evidence of the transition at $T_{N}$ is also seen in heat capacity data. The sharp peak in \textit{$\chi $(T)} and $C_{p}(T)$ moves to lower temperatures with increasing $H$. The $T_{N}$ is found to be strongly lowered by an applied field and $T_{N} \quad \sim $ 0 for H $\sim $ 70 kOe. Further work to understand the relative exchange couplings between various Cu atoms is currently in progress.