Solid state reaction at the interface between Heusler alloys and Al cap accelerated by elevated temperature and rough surface

We have investigated the solid state reaction at the interface of Co2Cr0.6Fe0.4Al, Co2FeSi, and Ni2MnGa Heusler alloy films and Al cap layers using x-ray absorption spectroscopy in transmission and total electron yield mode. At elevated temperatures and at rough surfaces the deposited Al severely reacts with the surface of a Heusler alloy indicated by changes of the absorption spectra. Microspectroscopy using photoemission electron microscopy reveals that the reaction proceeds inhomogeneously with reaction nuclei separated on a micron length scale.