Ferromagnetic/superconducting proximity effect in La_(0.7)Ca_(0.3)MnO_(3)/YBa_(2)Cu_(3)O_(7-δ) superlattices

We study the interplay between magnetism and superconductivity in high-quality YBa_(2)Cu_(3)O_(7)(YBCO)/La_(0.7)Ca_(0.3)MnO_(3)(LCMO) superlattices. We find evidence for the YBCO superconductivity depression in the presence of the LCMO layers. We show that due to its short coherence length, superconductivity survives in the YBCO down to a much smaller thickness in the presence of the magnetic layer than in low Tc superconductors. We also find that for a fixed thickness of the superconducting layer, superconductivity is depressed over a thickness interval of the magnetic layer in the 100 nm range. This is a much longer length scale than that predicted by the theory of ferromagnetic/superconducting proximity effect.