Magnetic pinning of flux lines in heterostructures of cuprates and manganites

Abstract

The magnetic properties of heterostructures of high-temperature superconducting $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ and highly spin polarized, ferromagnetic ${\mathrm{La}}_{2∕3}{\mathrm{Ca}}_{1∕3}\mathrm{Mn}{\mathrm{O}}_{3}$ that are electronically decoupled by a thin $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ layer are investigated by means of SQUID magnetometry. Below the transition temperature of the superconducting component the detected signal is a measure for the critical current in the superconductor. The obtained magnetic hysteresis loops at low temperatures exhibit a substantial asymmetry with respect to $H=0$. This can be understood in terms of pinning of flux lines in the superconducting film due to magnetic interaction with the ferromagnetic manganite layer.