Effects of Gd and Sm doping on the electronic structure and the superconductivity of (Ln = Gd and Sm)

The effects of Gd and Sm substitution on the Nd1.85−xLnxCe0.15Cu4±δ (Ln=Gd and Sm) single crystals have been studied by the X-ray-photoelectron spectroscopy (XPS) and resistivity measurements. It is found that such doping nominally does not change the doped carrier density, which is supported by a constant result of the ( I S / I M ). Gd doping leads to a weakness in the density of states at the Fermi level for superconducting Nd1.85−xGdxCe0.15Cu4±δ, while this phenomenon is not observed for Nd1.85−xSmxCe0.15Cu4±δ. This could have been resulted from the fact that Gd doping induces more localization than Sm doping does, and more localization may result in the suppression of T C for Gd doping and this has been observed with the resistivity measurements.