Hysteretic behavior of critical currents in heterostructures of high-temperature superconductors and ferromagnets

We have grown bilayer structures of the ferromagnet SrRuO 3 and the high-temperature superconductor YBa 2 Cu 3 O 7 − δ on single crystalline LaSrGaO 4 substrates by pulsed laser deposition. By means of quantitative magneto-optics, the critical current density in the superconducting film is measured and it is found that it strongly depends on the magnetization state of the ferromagnetic layer. The critical current density shows a hysteretic behavior that is strongly related to the magnetic hysteresis loop of the ferromagnet.