Spin resolved photoelectron spectroscopy of oxidic half-metallic ferromagnets and oxide-ferromagnet interfaces

Spin- and angle-resolved photoelectron spectroscopy was applied to study the spin-dependent electronic structure of the half-metallic ferromagnetic materials (Fe3O4 and CrO2) and bilayers I/FM (I = Al2O3 or MgO, FM = Fe(110)). Fe3O4 and CrO2 are found to be consistent with half-metallic ferromagnets, for the values investigated, with extraordinary high spin polarization values at the Fermi level. Our investigation of thin epitaxial Fe3O4(111) films at 300 K has shown the spin polarization of P = -(80 ± 5)% at EF which is consistent with the saturation magnetization of a thin epitaxial film, except for a small reduction, which can be attributed to, e.g., the excitation of spin waves near the surface. The agreement of the photoemission spectroscopy in [111] direction with density functional calculations, predicting an overall energy gap in the spin-up electron bands in high symmetry directions. In case of CrO2 our spin-resolved photoemission study of CrO2(100) films yields a spin polarization of approximately +(90±5)% at EF at 293K. This value and the magnitude of the gap in the spin-down states for values along the [100] direction are in good agreement with the prediction of the half-metallic nature of CrO2. The shape and the main features of the valence band photoemission spectra give a good agreement with recent LSDA+DMFT calculations. The oxidization process of thin aluminium films and the formation of epitaxial aluminium oxide layers (Al2O3) on the Fe(110) surface have been investigated in the present work. An approximately 1 ML thick alpha-Al2O3(0001) on Fe(110) showed a negative spin polarization of about -(17±5)% near EF which is an attenuated Fe(110) spin polarization due to scattering during the transport of the photoelectrons from Fe 3d states near EF through the Al-oxide layer.In case of the MgO/Fe(110) interface the spin-resolved PES experiments show that the spin polarization of the Fe(110) thin film abruptly decreases with increasing MgO film thickness. This behavior can not be ascribed to the scattering process of the spin-polarized photoelectrons in the MgO film. In this case the formation of a thin iron oxide (FeO) layer at the MgO/Fe interface was supposed and the thickness of this layer was estimated to be 1-1.5 ML.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Dedkov, Yuriy

Contributors dc:contributor

• Güntherodt, Gernot

• info:eu-repo/classification/ddc/530
• Physik
• half-metallic ferromagnet
• chromium dioxide
• magnetite
• spin-resolved
• PES

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121101%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59303