Cobalt spin state above the valence and spin-state transition in (Pr0.7Sm0.3)0.7Ca0.3CoO3

(Pr0.7Sm0.3)0.7Ca0.3CoO3 belongs to a class of cobalt oxides undergoing a first-order transition (T* close to 90 K) associated to a coupled change in the valence and spin-state degrees of freedom. The Curie-Weiss regime present around room temperature (T >> T*) was analysed in detail to address the controversial issue of the cobalt spin states above the transition. This magnetic investigation indicates that the Co4+ are in an intermediate spin-state, while the Co3+ are in a mixed state combining low-spin and high-spin states. These results are discussed with respect to the literature on related compounds and recent results of x-ray absorption spectroscopy.

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