Films of various iron oxides including FeO, Fe3O4, and agr;hyphen;Fe2O3were formed on the agr;hyphen;Al2O3(0001) surface by a reactive vapor deposition method and characterized by xhyphen;ray diffraction and conversion electron Mouml;ssbauer spectroscopy (CEMS). The formation range for each phase was determined as a function of the substrate temperature (Ts) and oxygen partial pressure (PO2). Typically, the deposition of (111)hyphen;oriented epitaxial magnetite films could be performed at low temperatures ofTs=523sim;623 K andPO2=1.0ndash;5.0times;10minus;4Torr. Good stoichiometry of the ashyphen;grown films were confirmed by CEMS, and the Verwey transition was clearly detected by measurements of resistivity and CEMS down to 77 K. However, the large lattice mismatch between the substrate and Fe3O4resulted in a columnar particle growth. The initially grown phase on such a mismatched substrate was specifically characterized by depositing the Mouml;ssbauer active isotope,57Fe, only at the deepest layers. On the other hand, by depositing57Fe only in the topmost layers, surface layers of wellhyphen;crystallized films have been found to be rather stable against oxidation.
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