Chemical pressure effect in CeFeAs1−xPxO0.95F0.05

We investigate the chemical pressure effect due to P doping in the CeFeAs1−xPxO0.95F0.05(0≤x≤0.4)(0≤x≤0.4) system. The compound CeFeAsO0.95F0.05 without P doping is on the boundary between antiferromagnet (AFM) and superconductor. The AFM order of Ce3+ local moments causes a significant reentrance behavior in both resistivity and magnetic susceptibility. Upon P doping, Tc increases and reaches a maximum of 21.3 K at x=0.15, and then it is suppressed to lower temperatures. Meanwhile, the AFM order of Ce3+ ions remains nearly the same in the whole doping range (0≤x≤0.4)(0≤x≤0.4). Our experimental results suggest a competition between superconductivity and Kondo effect in the Ce 1111 system.