PROBING SURFACE AND THIN-FILM MAGNETIC-STRUCTURE WITH CIRCULARLY-POLARIZED SYNCHROTRON-RADIATION

A new group of techniques predicated on the availability of a tunable source of circularly polarized soft x-rays show tremendous potential f or advancing the understanding of magnetic nanostructures. These techn iques involve use of circularly polarized radiation as probes in x-ray absorption and x-ray photoemission and photoelectron diffraction stud ies, and provide unique information about the element specific magneti c moments and magnetic structure of thin films, interfaces, and surfac es. Examples of each technique will be discussed with emphasis given t o the recently demonstrated first observation of spin-dependent photoe lectron diffraction using circularly polarized x-rays. This technique promises the direct, element specific determination of local magnetic structure on an atomic scale, and will be of tremendous utility in the effort to establish structure-property relationships in magnetic nano structures. Circularly polarized x-rays are used to produce spin-polar ized photoelectrons from the Fe 2p spin-orbit doublet. Intensity asymm etries of up to similar to 3% are observed for the 2P(3/2) sublevel. T hese asymmetries depend on the relative orientation of the x-ray polar ization vector and the sample magnetization as well as upon the photoe lectron kinetic energy and emission direction. Multiple scattering cal culations are found to reproduce both the observed energy and angular asymmetry variations. Strategies to increase the measured effect are a lso discussed. (C) 1996 American Vacuum Society.