Effects of Gd and Sm doping on the electronic structure and the superconductivity of Nd1.85−xLnxCe0.15CuO4±δ (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 (IS/IM). 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 TC for Gd doping and this has been observed with the resistivity measurements.