AC susceptibility measurements of films with different structural qualities

Abstract Superconducting ReBa 2 Cu 3 O 7 (R = Y, Er) epitaxial thin films were deposited by reactive laser ablation on YSZ (Yitria Stabilized Zirconia) and SrTiO 3 substrates under various conditions. The structural quality of the films were characterized by complete XRD measurements. The superconducting properties have been investigated by AC susceptibility in an extended AC fields range ( h AC ≤400 Oe). We focused our attention on the imaginary part χ ″( T ) (loss peak) for fields applied parallel and perpendicular to the film surface. The use of “high” parallel AC fields leads to a precise determination of the irreversibility lines (IL) in the ( h AC , T ) plane. The IL are weakly frequency 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.