Microwave properties of RE-Ni2B2C (RE = Y, Er) superconducting thin films

A comparative study of the microwave properties of YNi2B2C and ErNi2B2C sup erconducting films is reported. The measurements were performed using a mic rostrip resonator (f = 2 GHz) and a microwave cavity (f = 87 GHz). The anal ysis of the temperature dependence of the surface impedance Z(s) confirms t hat YNi2B2C compound is a conventional BCS (s-wave) superconductor On the c ontrary, ErNi2B2C samples show an anomalous behaviour in both the surface r esistance and penetration depth. This is tentatively ascribed to pair break ing effects on the superconducting density of states. A simplified generali sation of the Abrikosov-Gorkov theory, proposed by Machida, is successfully applied to describe the penetration depth data in the antiferromagnetic co mpound, while for the surface resistance granular effects cannot be ruled o ut. (C) 1999 Published by Elsevier Science B.V. All rights reserved.