Multiscale models of hard-soft composite media

The status of models of composite media for ultra-high density recording is reviewed. It is shown that the usual micromagnetic formalism may break down when dealing with interfaces where rapid spatial changes in magnetisation may occur. A multiscale approach is outlined, in which atomistic models are coupled with micromagnetic concepts to provide an improved physical model. The theory is applied to FePt/FeRh bilayers, which have potential as media for heat-assisted magnetic recording.