Magnetic characterization of YBCO thin films using low frequency AC suspeptometer

Low frequency ac-susceptibility measurements were made on laser ablated YBa2Cu3O7-δ epitaxial thin films by using a single spiral pick-up coil ac-susceptometer developed in our laboratory to study the role of oxygen content and weak-links on the magnetic behavior. The measurement of χ' and χ'' were made, in the temperature range of 15 to 100 K in the presence of applied field in the range 0.1 to 16 mT, on as-deposited and vacuum annealed samples. In the present paper, the observed modification of the absorption peak in the susceptibility data is correlated with the extent of deoxygenation and presence of weak-links in various samples. It was observed that in partially deoxygenated c-oriented thin films the YBCO grains were coupled through weak-links due to their relative in-plane rotation with respect to each other. These weak-links exhibit dependence on oxygen stoichiometry. This technique has potential for adoption as an on-line characterization technique to provide the values of Tc, ΔT, Jcmag and the volume fraction of the superconducting phases in thin films. (Authors)