Orientational phase transitions of a lattice of magnetic dots embedded in a London-typesuperconductor

Abstract

In recent experiments, structured arrays of ferromagnetic nanoparticles in the bulk ofa superconductor have been fabricated. We present the theory of orientationalphase transitions in a planar regular lattice of nanoscale ferromagnetic particlesembedded in a superconductor. In the London approximation, we show that theinteractions between ferromagnetic particles can lead to either a parallel or antiparallelspin alignment depending on the ratio of the interparticle distance, the Londonpenetration depth and the temperature. The extension of the results to systemsof ferromagnetic nanoparticles with more complicated geometries is discussed.