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arXiv · 1103.3646

Observation of a valence transition in (Pr,Ca)CoO3 cobaltites: charge migration at the metal-insulator transition

José Luis García-Muñoz·Carlos Frontera·Aura J. Barón-González·Sergio Valencia·Javier Blasco·Ralf Feyerherm·Esther Dudzik·Radu Abrudan·Florin Radu
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Abstract

X-ray absorption spectroscopy measurements in Pr0.5Ca0.5CoO3 and (Pr,Y)0.55Ca0.45CoO3 compositions reveal that the valence of praseodymium ions is stable and essentially +3 (Pr [4f 2]) in the metallic state, but abruptly changes when carriers localize approaching the oxidation state +4 (Pr [4f 1]). This mechanism appears to be the driving force of the metal-insulator transition. The ground insulating state of Pr0.5Ca0.5CoO3 is an homogeneous Co3.5-d state stabilized by a charge transfer from Pr to Co sites: 1/2Pr3+ + Co3.5 \to 1/2Pr3+2d + Co3.5-d, with 2d \approx 0.26 e-.

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José Luis García-Muñoz, Carlos Frontera, Aura J. Barón-González, Sergio Valencia, Javier Blasco, Ralf Feyerherm, Esther Dudzik, Radu Abrudan, Florin Radu. 2011-03-18. Observation of a valence transition in (Pr,Ca)CoO3 cobaltites: charge migration at the metal-insulator transition. https://doi.org/10.1103/physrevb.84.045104

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