Compositional variations in doped iron oxide magnetic thin films

Abstract

Iron oxide films are candidates for high-density thin-film disk storage media. The films are usually prepared by postdeposition oxidation to produce γ-Fe2O3. Films are usually doped to control grain size and coercivity. Recent work by polarized neutron reflection and Kerr rotation has shown that a magnetic dead layer sometimes exists at the γ-Fe2O3 surface. We have investigated such films by x-ray photoelectron spectroscopy (XPS), Auger spectroscopy, and Rutherford backscattering spectroscopy (RBS). The samples fall into two sets: Fe3p4 bulk composition and the γ-Fe2O3 films formed by postoxidation. 500-2600 A films were used. The γFe2ZO3 films, which show the magnetic dead-layer behavior, are shown by Auger and XPS in conjunction with Ar+ profiling to have a depleted Os or Co dopant level over the dead-layer depth. The Fe3O4 films have uniform dopant concentration profiles. For the Os doped films RBS at grazing angle provides quantitative nondestructive elemental composition analysis with a ~ 30-A depth resolution. The depletion of the Os at the surface for the γ-Fe2O3 films is confirmed and owing to the high Os cross section and good separation from the Fe signal excellent quantification is obtained. In addition RBS shows that though x-ray diffraction indicates nearly pure Fe3O4 and pure γ-Fe2O3 phases, the overall stoichiometries can deviate significantly. Finally some information on the chemical state of the dopant is provided from XPS data. © 1987, American Vacuum Society. All rights reserved.