AC SUSCEPTIBILITY MEASUREMENTS OF FILMS WITH DIFFERENT STRUCTURAL QUALITIES

Superconducting ReBa2Cu3O7 (R=Y, Er) epitaxial thin films were deposit ed by reactive laser ablation on YSZ (Yttria Stabilized Zirconia) and SrTiO3 substrates under various conditions, The structural quality of the films were characterized by complete XRD measurements. The superco nducting properties have been investigated by AC susceptibility in an extended AC fields range (h(AC)less than or equal to 400 Oe). We focus ed our attention on the imaginary part chi ''(T) (loss peak) for field s applied parallel and perpendicular to the film surface. The use of ' 'high'' parallel AC fields leads to a precise determination of the irr eversibility lines (LL) in the (h(AC), T) plane. The IL are weakly fre quency dependent and exhibit a nearly linear behavior. The observation of fine structures of the loss peak are correlated to the presence of different phases and/or grain orientations.