NEUTRON AND X-RAY SCATTERING STUDIES OF THIN FILM ALLOYS AND MULTILAYERS M. B. Salamon*, Department of Physics, University of Illinois at Urbana/Champaign, *Center for Materials Science, MS K765, Los Alamos National Lab, Los Alamos, NM 87545

The growth of magnetic materials by molecular beam epitaxy results in synthetic crystals with novel properties induced by the periodic variation of composition, and by the physical constraints imposed by coherency strains and epitaxial clamping to a substrate. Among the most dramatic effects is the observation of long-range coupling of transverse helical magnetization and longitudinal sinusoidal modulation through non-magnetic materials such as Y and Lu. As first step in measuring directly the induced magnetization, we have demonstrated that resonant x-ray scattering is capable of detecting a spin-polarization of the order of 0.1 (u_B/atom on non-magnetic atoms in alloys where the dominant magnetization is 100 times larger. Attempts to detect these effects in superlattices of Dy and Lu and Ho and Lu are complicated by magnetostrictive effects and changes in the intensity of superlattice Bragg peaks on passing through an absorption edge. A second thrust of our research is directed toward control of structure through epitaxy. We will demonstrate the stabilization of the dhcp phase of a NdY alloy in the composition range where the Sm structure is the equilibrium phase. Surprisingly, we have found that the helimagnetic phase present in the alloy persists in superlattices, where it competes with the complex basal-plane ordering of Nd.