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Transport properties and spin correlations of La<sub>1</sub><sub>.</sub><sub>8</sub><sub>5</sub><sub>-</sub><sub>x</sub>Sr<sub>0</sub><sub>.</sub><sub>1</sub><sub>5</sub><sub>+</sub><sub>x</sub>Cu<sub>1</sub><sub>-</sub><sub>x</sub>Fe<sub>x</sub>O<sub>4</sub>

American Physical Society
Publication Date
  • 5-I Nano


A series of double-doped La1.85-xSr0.15+xCu1-xFexO4 (0less than or equal toxless than or equal to1) ceramic samples were prepared by the solid-state reaction method. The structure, transport properties, and spin correlations were studied by means of x-ray diffraction, resistivity, thermoelectric power (TEP) and electron spin resonance (ESR). Double doping causes an increase of the lattice parameter a and a decrease of c. A great discrepancy of the thermal activation energy is derived from the resistivity and TEP at high doping levels, which can be understood in terms of a polaron model. The ESR result indicates that the double doping influences the spin correlation of the CuO2 plane markedly, which suggests that the Fe3+ spins change from localization to delocalization as x increases from low doping to high doping. A close relation between localized spin scattering and the broad peak in the TEP versus T curve is proposed. A comparison of the transport mechanism between the Fe doped and the Co and Ni doped La214 systems is given in this paper.

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