Superconductivity in LaFeAs1-xPxO: Effect of chemical pressures and bond covalencyCao Wang1, Shuai Jiang1, Qian Tao1, Zhi Ren1, Yuke Li1, Linjun Li1, Chunmu Feng2, Jianhui Dai1, Guanghan Cao1 and Zhu-an Xu1
1 Department of Physics, Zhejiang University - Hangzhou 310027, China
2 Test and Analysis Center, Zhejiang University - Hangzhou 310027, China
received 9 April 2009; accepted in final form 27 April 2009; published May 2009
published online 26 May 2009
We report the realization of superconductivity by an isovalent doping with phosphorus in LaFeAsO. X-ray diffraction shows that, with the partial substitution of P for As, the Fe2As2 layers are squeezed while the La2O2 layers are stretched along the c-axis. Electrical resistance and magnetization measurements show emergence of bulk superconductivity at ~ 10 K for the optimally doped LaFeAs1-xPxO (x = 0.25–0.3). The upper critical field at zero temperature is estimated to be 27 T, much higher than that of the LaFePO superconductor. The occurrence of superconductivity is discussed in terms of chemical pressures and bond covalency.
74.70.Dd - Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.).
74.62.Bf - Effects of material synthesis, crystal structure, and chemical composition.
74.62.Dh - Effects of crystal defects, doping and substitution.
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