The effect of Cu/Zn substitution in Nd 1.85Ce 0.15CuO 4 on superconductivity studied by magnetic, transport and specific heat measurements and Raman spectroscopy

Abstract

We report on the structural chemistry, DC and AC magnetic, magnetoresistance, specific heat and Raman measurements of Cu/Zn substituted Nd 1.85Ce 0.15CuO 4. Single phase solid solutions of Nd 1.85Ce 0.15Cu 1− x Zn x O 4− δ were observed for x≤0.05 with the Nd 2CuO 4-type and with a random distribution of (Nd, Ce) and (Cu, Zn) on their respective lattice sites. Cu/Zn substitution suppresses superconductivity with an initial rate of −4.5 K/mol% Zn. With increasing x, the critical fields and critical current densities are strongly reduced whereas the number of effective pinning centers increases. The normal state electronic specific heat coefficient is estimated to be 11 mJ/(mol K 2). Anomalies of the resistivity and magnetoresistance are discussed in terms of a two-dimensional superconducting network in the perlocation regime. Raman spectroscopy indicates that with increasing Zn content the oxygen at the 4d site slightly displaced from the original position in the x− y plane.