Magnetic vortex pinning in superconductor/ferromagnet nanocomposites

This paper discusses the hysteretic vortex pinning recently observed in superconductor/ferromagnetic nanocomposites. We show that in nanocomposite thin films consisting of Gd particles incorporated in a Nb matrix the hysteresis and pinning are associated with magnetic reversal losses in the Gd particles. This mechanism is fundamentally different in origin to other magnetic pinning interactions previously proposed for ferromagnetic particles or other microstructural features. We demonstrate that this mechanism has wider relevance and may have been observed previously.