Low-temperature anomalies of the superconducting properties of Nd1.85Ce0.15CuO4-y

We have measured the temperature dependence of the change Delta lambda(ab)( T) = lambda(ab)(T) - lambda(ab)(T = 0) of the in-plane London penetration d epth lambda(ab) in the electron-doped cuprate superconductor Nd1.85Ce0.15Co O4-y (NCCO). An anomalous temperature dependence below about 4 K is observe d. In contrast to the expected monotonous decrease of lambda(ab)(T) With de creasing temperature, lambda(ab)(T) is found to increase with decreasing te mperature below 4 K resulting in a non-monotonous overall temperature depen dence. This anomalous behavior was found to be absent in analogous measurem ents performed on Pr1.85Ce0.15CoO4-y (PCCO). From this, we conclude that th e anomalous behavior of NCCO is caused by the influence of the Nd3+ magneti c moments. Correcting for the temperature-dependent susceptibility due to t he Nd3+ moments, an exponential lambda(ab)(T) dependence is obtained indica ting s-wave pairing in the electron-doped superconductors. (C) 2000 Elsevie r Science B.V. All rights reserved.