Magnetism and superconductivity in La0.7Ca0.3MnO3/YBa2Cu3O7-delta 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 super conductivity for YBCO layer thickness in excess of 4 unit cells. The critic al temperature increases with YBCO thickness, and a T-c of 58 K is found fo r a YBCO thickness of 10 unit cells. Magnetization measurements show a ferr omagnetic transition at 100 K in a (LCMO6 u.c./YBCO5 u.c.)(15 bilayer) supe rlattice, and a depressed value of the saturation magnetization of 20 emu c m(-3). These results are discussed in terms of interface disorder (analyzed by x-ray diffraction and transmission electron microscopy) and of the poss ible interaction between magnetism and superconductivity. (C) 2001 American Institute of Physics.