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Evidence for Multiple Phase Transitions in La1-xCaxCoO3

M. Kriener, M. Braden, D. Senff, O. Zabara, T. Lorenz

cond-mat.str-elarXiv:cond-mat/0605721

Abstract

We report thermal-expansion and specific-heat data of the series La1-xCaxCoO3 for 0 <= x <= 0.3. For x = 0 the thermal-expansion coefficient alpha(T) features a pronounced maximum around T = 50 K caused by a temperature-dependent spin-state transition from a low-spin state (S=0) at low temperatures towards a higher spin state of the Co3+ ions. The partial substitution of the La3+ ions by divalent Ca2+ ions causes drastic changes in the macroscopic properties of LaCoO3. Around x ~ 0.125 the large maximum in alpha(T) has completely vanished. With further increasing x three different anomalies develop.

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