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

Aura J. Bar\'on-Gonz\'alez; Carlos Frontera; Esther Dudzik; Florin Radu; Javier Blasco; Jos\'e Luis Garc\'ia-Mu\~noz; Radu Abrudan; Ralf Feyerherm; Sergio Valencia

arxiv: 1103.3646 · v1 · pith:7D2DVNQPnew · submitted 2011-03-18 · ❄️ cond-mat.mtrl-sci

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

Jos\'e Luis Garc\'ia-Mu\~noz , Carlos Frontera , Aura J. Bar\'on-Gonz\'alez , Sergio Valencia , Javier Blasco , Ralf Feyerherm , Esther Dudzik , Radu Abrudan

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Florin Radu

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classification ❄️ cond-mat.mtrl-sci

keywords coo3statetransitionchargemetal-insulatorvalenceabruptlyabsorption

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

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