Engineering magnetic materials on the atomic scale (invited)

Abstract
Ultrahigh vacuum (UHV) systems and the use of atomic beams for deposition of atoms layer by layer combine to make possible the creation of new materials. The applications to metallic magnetism are gaining increasing attention. The building of sandwiches of magnetic and nonmagnetic layers should lead to increased understanding of the propagation of spin polarization through metals and the effects of finite thickness on the ground state properties and the thermodynamics of magnetic materials. The most important step in this process is in the first layer, i.e., the preparation of the substrate and the determination of the quality of the interface and of the overlayer. The techniques of surface science, e.g., residual gas analysis (RGA), reflection high energy electron diffraction (RHEED), Auger electron spectroscopy (AES), and x-ray photoemission spectroscopy (XPS) are essential for the characterization of the interface. Illustrations of these include our own work on body-centered-cubic Ni deposited epitaxially on (100)Fe with and without intermediate epitaxial Au layers and with and without Au cover layers, studied using ferromagnetic resonance (FMR). The engineering of new magnetic phases takes into account the tendency of increased atomic volume to enhance magnetic moments. Epitaxy can be used to create negative pressures. New phases of Mn have been formed using the (0001) surface of Ru as a template for expanded structures.