Publication Details

Wang, C., Li, Y. K., Zhu, Z. W., Jiang, S., Lin, X., Luo, Y. K., Chi, S., Li, L. J., Ren, Z., He, M., Chen, H., Wang, Y. T., Tao, Q., Cao, G. H. & Xu, Z. A. (2009). Effects of cobalt doping and phase diagrams of LFe1-xCox AsO (L=La and Sm). Physical Review B: Condensed Matter and Materials Physics, 79 (5),


The superconducting phase diagrams have been established by the measurements of electrical resistivity, magnetic susceptibility, and thermopower in cobalt-doped LFeAsO (L=La and Sm) systems. It is shown that the antiferromagnetic spin-density-wave order in the parent compounds is rapidly suppressed by Co doping, and superconductivity emerges at x=0.025 and 0.05 in LaFe1−xCoxAsO and SmFe1−xCoxAsO, respectively. The Tc(x) curves of both systems are domelike, with a maximum Tc of 13 K at x=0.075 in LaFe1−xCoxAsO and 17.2 K at x=0.1 in SmFe1−xCoxAsO. Thermopower measurement shows dominant electron-type transport for the Co-doped samples, in accordance with itinerant character of Co 3d electrons. We found a close correlation between Tc and the abnormally enhanced part of normal-state thermopower. The occurrence of superconductivity via the Fe-site doping in the iron-based oxyarsenide contrasts sharply with the destruction of superconductivity by the Cu-site (within CuO2 planes) doping in high-temperature superconducting cuprates.

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