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We investigate the superconducting transition temperature of epitaxial La0.7Sr0.3MnO3/YBa2Cu3O7/ La0.7Sr0.3MnO3 (LSMO/YBCO/LSMO) trilayers as a function of the magnetic field parallel to the layer structure. In these structures, the magnetic moment of the half-metallic ferromagnet LSMO is parallel to the plane of the film. The coercivity-and saturation field of the top and bottom LSMO layer could be independently tuned by adjusting their thickness. The application of a magnetic field increased the superconducting transition temperature by about 1.6 K with respect to the demagnetized state of the LSMO. Three possible mechanisms of the enhancement are considered. These are the stray fields due to domain walls, spin polarization of the current, and the formation of an odd triplet superconducting state.

The FeSe samples in the form of polycrystals, single crystals and thin films have been prepared and characterized. The synthesized material has been hot isostatically pressed under pressure of 0.45 GPa of 5N purity argon with the use of the high gas pressure trap system (HGPTS). Thin films have been fabricated by the mixed procedures with the use of DC sputtering from various types of targets and processed employing the HGPTS. The used HGPTS assures a full separation of the active volume for synthesis or crystal growth of material and the inert gas medium. The obtained FeSe 0.88 samples have T c between 8 and 12 K. The samples have been characterized by SEM, EDX, XRD, magnetic susceptibility and resistivity measurements.