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

• (Pr0.7Sm0.3)0.7Ca0.3CoO3 exhibits a valence and spin state transition at T* ≈90 K.
• The magnetic susceptibility shows a Curie–Weiss regime at T >> T*.
• Co4+ is found to be in an intermediate spin-state.
• Co3+ is found to be in a mixed state combining low- and high-spin states.

(Pr0.7Sm0.3)0.7Ca0.3CoO3 belongs to a class of cobalt oxides undergoing a first-order transition (T* ≈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 analyzed 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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