Spin-Resolved Electron Spectroscopy of Epitaxially Grown Magnetite on Magnesium Oxide (001)

A unique angle-, energy-, and spin-resolved electron spectroscopy instrument for the study of magnetic surface systems is presented. Detailed design considerations are discussed, with an emphasis on providing the instrumental parameters required for performing spin-resolved electron energy loss spectroscopy (SREELS). The principles of energy -dispersive energy analysis and Mott spin-polarimetry are outlined. Sample alignment and signal chain optimization procedures are described, and spectrometer and polarimeter calibration is addressed. The synthesis of magnetite films of magnesium oxide (001) using oxygen plasma assisted molecular beam epitaxy is discussed. Characterization of such films using SQUID magnetometry and X-ray diffraction is discussed. Strategies for cleaning films in vacuo are discussed. Spin-resolved secondary emission spectroscopy (SRSEES) of the synthesized films is discussed. Secondary emission cascade polarization enhancement is shown to reflect the semi-metallic spin-structure of magnetite. The polarization plateau of the spin-resolved secondary emission reflects the average 3-d band polarization of stoichiometric rm Fe_3O_4 as determined by spin-resolved band structure. Fine structure is seen in the SRSEES spectrum, and models of the low energy spin -polarization enhancement are discussed in relation to the semi-metallic nature of rm Fe_3O_4 . Spin-resolved Auger emission spectroscopy (SRAES) of the synthesized systems is discussed, with special attention to correlation effects in the valence-valence Auger transitions. Suppressed intensity and polarization of the Fe rm M _{23}M_{45}M_{45 } Auger emission relative to the Fe rm M_1M_{45}M_{45 } Auger emission is observed. Very strong resonant emission with shake up is observed. Oxygen LMM emission is used to verify the surface cleanliness of the present samples. No spin-polarization was detected in the oxygen Auger features.