Cuprate based oxide superlattices showing simultaneously superconducting and ferromagnetic properties

Superconductivity and ferromagnetism are antagonistic ordering phenomena and their coexistence in a material requires a spatial separation of the electronic systems giving rise to each of them. All oxide superlattices are good candidates to study the electronic interaction of superconductivity and ferromagnetism. Several types of YBa₂Cu₃O_7-x/La₂3/Ca₁3/MnO₃ as well as YBa₂Cu₃O_7-x/SrRuO₃ superlattices have been prepared by pulsed laser deposition and a reduction of both ordering temperatures as a function of superlattice composition has been studied. For the explanation of the results several novel concepts have to be developed based on a long-range ferromagnetic interlayer coupling and a novel long-range superconducting proximity effect.