The structural characterisation of molecular beam epitaxy-grown exchange-biased bilayers

Abstract

NiFe/FeMn exchange-biased thin films were grown in an applied magnetic field of approximately 200 Oe using molecular beam epitaxy. In order to obtain the optimum conditions for the epitaxial growth of the thin films, various chemical treatments of the Si(1 1 1) substrates and insertion of a Cu buffer layer were used. The 7×7 surface reconstruction of Si(1 1 1) was found out to be the crucial factor for the epitaxial growth. This surface promotes the reaction of Si with the Cu buffer layer to form epitaxial η″-Cu 3Si which then allows good epitaxy of NiFe and FeMn. In situ reflection high-energy electron diffraction and high resolution electron microscopy observation confirmed the epitaxial growth of the films to be of high quality with well defined flat interface between the layers.