SURFACE-RESISTANCE AND PENETRATION DEPTH ANOMALIES NEAR THE SUPERCONDUCTING TRANSITION IN YBCO THICK-FILMS AT LOW-FREQUENCIES

During the normal-superconductor transition, surface resistance and pe netration depth peak anomalies have: been observed in YBCO thick films on Zi(Y)O-2 substrates, between 1 kHz and 1 MHz frequencies. The reso nance curve-like anomaly's amplitude depends linearly upon the frequen cy and not on the thickness of the film. It is not connected directly to the film's intrinsic superconductivity properties, such as T-c and J(c), and is not sensitive to the direction of the temperature sweep. The penetration depth presents a lambda alpha f(-1) frequency dependen ce. The frequency dependence of the AC flux penetration's onset temper ature is in agreement with that predicted by the vortex-glass model. W e believe the anomaly could arise from the competition between the tem perature dependence of the critical current density and that of the mi xed state's volume.