Epitaxial MgO/Fe(001) and Fe/MgO(001): Structures of the interfaces

Abstract

The chemical, electronic and magnetic structures of the interfaces between Fe(001) and MgO(001) thin films were studied using conversion electron Mössbauer spectroscopy (CEMS). A 1 ML thick 57Fe probe located at either of the interfaces in the MgO/56Fe/MgO epitaxial structure enabled precise measurements of the interfacial hyperfine interactions. Analysis of the CEMS spectra showed that both the “MgO/Fe” and “Fe/MgO” interfaces are partially oxidized (63% and 86%, respectively), although, despite good crystallinity, no well-defined iron oxide phases were detected. At the “MgO/Fe” interface, 14% of the oxidized Fe sites were found to be defective (located at steps, corners or kinks). The “Fe/MgO” interface, from which the formation of 57Fe islands of at least 3 ML in height was inferred, was found to be almost defect-free. No modification of the hyperfine parameters of Fe atoms located away from the interface was detected for “Fe/MgO,” in contrast with the “MgO/Fe” interface. Approximately 6% of the probe layer diffused into the MgO films at both interfaces.