Phase diagram of the NdFe1-xRhxAsO superconductor

Polycrystalline samples with a nominal composition of NdFe1-xRhxAsO (0 <= x <= 0.25) were synthesized using a solid state reaction method. Bulk superconductivity with a maximum Tc = 13 K is observed in the x = 0.1 sample. A temperature-composition phase diagram is established for the NdFe1-xRhxAsO system based on the electrical resistivity and magnetization measurements. A first-order-like transition from an antiferromagnetic state to the superconducting state at a critical Rh-doping point xc = 0.045 is observed in the present phase diagram. The value for the upper critical field Hc2(0) is estimated to be about 26 T for the x = 0.10 sample by using the WHH theory.