Magnetism and superconductivity in La_(0.7)Ca_(0.3)MnO_(3)/YBa_(2)Cu_(3)O_(7-δ) superlattices

We report on the magnetic and superconducting properties of La_(0.7)Ca_(0.3)MnO_(3)/YBa_(2)Cu_(3)O_(7) (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 T_(c) of 58 K is found for a YBCO thickness of 10 unit cells. Magnetization measurements show a ferromagnetic transition at 100 K in a (LCMO_(6u.c.)/YBCO_(5 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