Magnetism and superconductivity in La0.7Ca0.3MnO3/YBa2Cu3O7−δ superlattices

We report on the magnetic and superconducting properties of La0.7Ca0.3MnO3/YBa2Cu3O7 (LCMO/YBCO) superlattices. For a constant LCMO layer thickness of 6 unit cells (u.c.), resistance and susceptibility measurements show superconductivity for YBCO layer thickness in excess of 4 unit cells. The critical temperature increases with YBCO thickness, and a Tc of 58 K is found for a YBCO thickness of 10 unit cells. Magnetization measurements show a ferromagnetic transition at 100 K in a (LCMO6 u.c./YBCO5 u.c.)15 bilayer superlattice, and a depressed value of the saturation magnetization of 20 emu cm−3. These results are discussed in terms of interface disorder (analyzed by x-ray diffraction and transmission electron microscopy) and of the possible interaction between magnetism and superconductivity.