Effects of phosphorous doping on the superconducting properties of SmFeAs(O,F)

Abstract The systematic doping effect induced by the isovalent substitution of P for As on the superconducting properties of F-doped SmFeAsO 0.88 F 0.12 (Sm1111) has been studied by physical and magnetic measurements. The cell volume ( V ) decreases with P doping and the anisotropic chemical pressure might be induced. However, the superconducting transition temperature ( T c ) and the upper critical field ( H c2 ) are suppressed. Thermoelectric power ( S ) indicates the majority of electron type charge carriers in support of Hall measurements and its magnitude does not change very much for different P concentrations. The present investigation depicts that isovalent substitutions in the FeAs layer strongly deteriorate the superconducting properties of Sm1111 as a result of increase in chemical pressure. These isovalent substitution effects are comparatively discussed with hole (Mn) and electron (Ni) type substitutions in the superconducting layer of Sm1111.