Quantitative magneto-optical analysis of twinnedYBa2Cu3O7−δ/La1−xSrxMnO3 bilayers

Abstract

Magneto-optical analysis was performed onYBa2Cu3O7−δ/La1−xSrxMnO3 bilayers grown ontwinned LaAlO3 substrates. Thetwin boundaries in the LaAlO3 substrate induced splitting of the manganite magnetic domains with either in-plane or out-of-planemagnetization, depending on the strontium doping level affecting the magnetic pattern. In theYBa2Cu3O7−δ film, the spontaneous vortex phase, as induced by the out-of-plane magnetic moments inthe manganite films, was directly visualized. For vortices nucleated by an externalmagnetic field, we distinguished different vortex dynamics due to the out-of-planemagnetic moments located either in correlated defects (twin boundaries) or in ahomogeneous part of the heterostructure. Vortex guidance over the magnetic domains,dependent only on the relative orientation of the vortex driving force with respectto the local out-of-plane magnetization in the manganite layer, was observed.By means of the inversion of the Biot–Savart law, the local modulations of thesupercurrent by the spontaneous vortex phase were imaged. Moreover, a localenhanced/depressed critical current was found across domains of opposite magneticpolarization.