CIRCULAR-DICHROISM IN 4F PHOTOEMISSION FROM MAGNETICALLY ORDERED RARE-EARTH MATERIALS

4f Photoemission (PE) spectra from magnetically ordered rare-earth mat erials using circularly polarized X-rays exhibit strong Magnetic Circu lar Dichroism (MCD), i.e., the intensities of the individual multiplet lines depend on the relative orientation of sample magnetization and photon spin. On the example of the well-resolved Tb 4f PE multiplet, i t is shown that in relevant cases 4f PE lines are essentially only obs erved for one magnetization direction, either parallel or antiparallel to the photon spin. These large MCD effects in 4f PE open new perspec tives in the analysis of surface and thin-film magnetism and provide a sensor for the degree of circular polarization of soft X-rays over a wide photon-energy range. To demonstrate the potential of MCD in 4f PE as a magnetometer, we studied Gd(0001) and Tb(0001), where the magnet ization of the topmost atomic (0001) layer can be easily separated fro m the bulk magnetization via the surface core-level shift. In multicom ponent magnetic thin films containing different rare-earth elements, 4 f PE allows to monitor magnetization in an element-specific way, e.g., in case of the hetero-magnetic interface 1ML Eu/Gd(0001).