Spin-resolved electron spectroscopies of epitaxial magnetite (001) (abstract)

Abstract

We will present the first spin-resolving electron spectroscopic studies of a magnetite (Fe3O4)(001) surface. Magnetite is a semimetal with a high density of states in the minority band, but a large band gap in the majority states at the Fermi energy. The polarization of the secondary emission cascade is measured using spin-resolved secondary electron emission spectroscopy (SRSEES), and reflects the semimetallic spin structure of Fe3O4. The polarization plateau of spin-resolved secondary emission (29.8%) matches the average 3D band polarization of stoichiometric Fe3O4 as determined from spin-resolved band structure calculations (34.2%). An enhancement of the polarization of the secondary electrons at lowest energies will also be discussed. Spin-resolved Auger emission spectroscopy (SRAES) of the Fe3O4 films have been measured and show correlation effects in the valence-valence Auger transitions. Suppressed intensity and polarization of M23M45M45 Auger emission relative to M1M45M45 Auger emission is observed, as well as strong resonant emission with shake-up. Conversely, no spin polarization is detected in the spin-resolved oxygen LMM Auger features, although oxygen Auger emission (in which we can distinguish between adsorbed and bonded oxygen) is used to verify surface cleanliness of the samples. The synthesis of Fe3O4 films grown on magnesium oxide (001) substrates using oxygen plasma-assisted molecular beam epitaxy will be discussed, as will thin-film characterization using SQUID magnetometry and x-ray and electron diffraction. A unique angle-, energy-, and spin-resolved electron spectrometer has been designed and built for the study of magnetic surfaces, and these studies represent its’ first use. That spectrometer is based on a tandem configuration of an energy-dispersive energy analyzer and Mott spin polarimeter.