Spin-state transition, magnetic, electrical and thermal transport properties of the perovskite cobalt oxide Gd0.7Sr0.3CoO3 |
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Authors: | R. Ang X.B. Zhu X.G. Luo |
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Affiliation: | a Key Laboratory of Materials Physics, Institute of Solid State Physics, and Hefei High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, People's Republic of China b Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China |
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Abstract: | The magnetization, resistivity ρ, thermoelectric power (TEP) S, and thermal conductivity κ in perovskite cobalt oxide Gd0.7Sr0.3CoO3 have been investigated systematically. Based on the temperature dependence of susceptibility χg(T) and Seebeck coefficient S(T), a combination of the intermediate-spin (IS) state for Co3+ and the low-spin (LS) state for Co4+ can be suggested. A metal-insulator transition (MIT) caused by the hopping of σ* electrons (localized or delocalized eg electrons) from the IS Co3+ to the LS Co4+ is observed. Meanwhile, S(T) curve also displays an obvious phonon drag effect. In addition, based on the analysis of the temperature dependence of S(T) and ρ(T), the high-temperature small polaron conduction and the low-temperature variable-range-hopping conduction are suggested, respectively. As to thermal conduction κ(T), rather low κ values in the whole measured temperature range is attributed to unusually large local Jahn-Teller (JT) distortion of Co3+O6 octahedra with IS state. |
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Keywords: | 75.30.Kz 72.20.Pa 71.30.+h |
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