Studies of Ultrathin Magnetic Films Using Synchrotron Radiation: Resonant Photoemission, Circular and Linear Magnetic Dichroism.
Date of Award
Doctor of Philosophy (PhD)
Physics and Astronomy
Richard L. Kurtz
The work described in this dissertation is a study of the relationship between structural, electronic, and magnetic properties of ultrathin films of 3d-transition metals grown epitaxially on Cu substrate. The two systems that we have studied are films of fcc-Co on Cu(001) and Cu(111) and Fe and oxidized Fe films on Cu(001). Both systems are either employed or have potential applications in the data storage industry. In order to provide information on the inter-relationship between the electronic structure and magnetic properties, we present results of magnetic dichroism observed in photoemission from the valence-bands and the shallow 3p core levels of ultrathin films grown on Cu. We have used both linearly and circularly polarized light from the Center for Advanced Microstrucutres and Devices (CAMD) synchrotron source and observe the angular distributions of the photoemitted electrons using a display type analyzer. Magnetic Circular Dichroism (MCD) and Magnetic Linear Dichroism (MLD) phenomena in UV and "soft" X-ray photoemission were observed in the core and valence-band structures of atomically thin Co/Cu(001), Fe/Cu(001) and Co/Cu(111). The patterns of the magnetic dichroism asymmetry in angular distributions of the photoelectrons in the valence-band photoemission will be discussed. A broad array of techniques including ARUPS, constant initial state (CIS) resonant PES and STM were used to characterize Fe/Cu(001) interface oxidized at elevated temperature. The specific oxide phase, whether FeO(111) or Fe 3O4(111) that forms depends on the initial Fe thickness. Both core level and valence band photoemission data will be presented. Difference spectra show that the interfaces of these films have a metallic density of states at EF, unlike any of the bulk phases of iron oxide. Core level photoemission from Fe 3p levels shows the existence of two distinct Fe oxidation states. CIS resonant photoemission data show that the DOS close Fermi edge can be identified as is mostly due to a contribution of iron oxide states, but not due to Cu states. MCD/MLD data suggest a significant degree of spin polarization at the Fermi edge and a presence of a surface magnetization for these films.
Koveshnikov, Alexey Nikolaevich, "Studies of Ultrathin Magnetic Films Using Synchrotron Radiation: Resonant Photoemission, Circular and Linear Magnetic Dichroism." (2001). LSU Historical Dissertations and Theses. 351.