The enhancement of flux-line pinning in all-oxide superconductor/ferromagnet heterostructures

We have studied the local critical current density, jc, in the superconductor thin film of bilayer structures consisting of YBa2Cu3O7 and the ferromagnets La2/3Ca1/3MnO3 and SrRuO3, respectively, by means of quantitative magneto-optics. A pronounced hysteresis of jc was observed which is ascribed to the magnetization state of the ferromagnetic layer. The results are discussed within the frame of magnetic vortex–wall interactions.