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 Nd(1.85-x)Ln(x)Ce(0.15)Cu(4 +/-delta) (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 Nd(1.85-x)Ln(x)Ce(0.15)Cu(4 +/-delta), while this phenomenon is not observed for Nd(1.85-x)Ln(x)Ce(0.15)Cu(4 +/-delta). 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. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.