Magnetic depth profiles of complex oxide F/S/F trilayers.

The origin of the large magnetoresitance in epitaxial F/S/F trilayers composed of highly spin polarized ferromagnetic La$_{0.7}$Ca$_{0.3}$MnO$_{3}$ and high-T$_{c}$ superconducting YBa$_{2}$Cu$_{3}$O$_{7-\delta }$ (YBCO) is investigated by characterizing the magnetic structure. Polarized neutron reflectometry experiments have determined the detailed magnetization depth profiles in trilayers with varying YBCO layer thicknesses. In addition to inhomogeneous magnetization profiles, rotation of the magnetization during the magnetization reversal for the films with thick ($\ge $ 17.7 nm) YBCO layers has been observed. The results are consistent with the presence of an (in plane) easy-axis tilted away from the (100) direction.