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

TL;DR

This study investigates the spin states of cobalt in (Pr0.7Sm0.3)0.7Ca0.3CoO3, revealing intermediate and mixed spin states above the valence and spin-state transition at around 90 K, using magnetic and spectroscopic analysis.

Contribution

It provides detailed insights into the cobalt spin states above the transition, clarifying previous controversies through magnetic and spectroscopic data.

Findings

Co4+ ions are in an intermediate spin state

Co3+ ions are in a mixed low-spin and high-spin state

Results align with recent x-ray absorption spectroscopy studies

Abstract

(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.