W:awardsawards97 9701409 Tonner This renewal project will study the structural and magnetic properties of metastable magnetic ultrathin films of transition metals, grown under controlled conditions by ultra-high vacuum physical vapor deposition and by sputter-deposition. Growth conditions will be chosen to produce novel crystal structures, which are not ordinarily found in the bulk phase diagram. We combine structural and magnetic measurements to correlate changes in the magnetic phase diagram with surface crystallography and morphology. Multiple structural techniques are employed, including quantitative electron and photoelectron diffraction, and surface x-ray diffraction. Magnetic measurements are primarily done using circularly polarized soft x-ray circular dichroism. The emphasis is on ultrathin binary alloys, coupled ferromagnetic bilayers, and 'wedge' and 'sandwich' nanostructures. %%% This is a renewal project in which modern techniques of crystal growth will be used to create magnetic nanostructures which have unique and surprising properties. We are searching for ways to produce magnetic materials that can be useful in a new generation of computer digital electronics. These devices, called spin-valves or spin-transistors, use magnetism in the way that the older transistor uses electronic charge. Since the magnetic information can be stored for long periods without the need for an external power source, spin-valves are attractive as a new type of computer memory device for portable computers. The physical properties which are desirable for a high efficiency spin valve require us to control the growth of magnetic layers with atomic precision. The magnetic behavior of these metastable, ultrathin, magnetic films can be completely different from that of an ordinary 'bulk' material. We are studying the relationship between structure and magnetic properties, to develop ways of predicting and optimizing ultrathin mag nets for spin valves. ***
