The spin-flip transition of 1000 Å-thick α-Fe2O3 films was investigated by conversion electron Mössbauer spectroscopy from 2.5 to 673 K. The films were epitaxially formed on α-Al2O3 single-crystalline substrates by a reactive vapor deposition method. Not only the transition temperature but also the spin axis were found to strongly depend upon the film orientation, probably as a result of anisotropic lattice strains caused by interactions with the substrate. For a (102)-oriented film the transition takes place at about 400 K, much higher the Morin transition temperature (260 K) of the free crystal, and the spin axis lying within the (102) plane above 400 K changes almost normal to the plane at room temperature and below: the normal makes 57.6° with the spin axis of the free crystal. A (001)-oriented film, on the other hand, does not show any transition at least down to 2.5 K.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics