Ultraviolet Raman spectroscopy of epitaxial ScFeO$_{\mathrm{3}}$ films

Scandium ferrite, ScFeO$_{\mathrm{3}}$ is a recently discovered multiferroic, i.e. a material that exhibits coexisting ferroelectric and magnetic ordering. 10 and 100 nm-thick ScFeO$_{\mathrm{3}}$ films grown by molecular-beam epitaxy on (0001) Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ substrates have been studied by variable temperature ultraviolet Raman spectroscopy. ScFeO$_{\mathrm{3}}$ spectra at room temperature are consistent with the polar hexagonal \textit{P6}$_{3}$\textit{cm} structure. The temperature evolution of the Raman spectra of a ScFeO$_{\mathrm{3}}$ film measured in the range 10--1300 K indicate a transition to a non-polar (likely \textit{P6}$_{3}$\textit{/mmc}) phase; fitting of the temperature dependence of the Raman intensities yields a transition temperature of 900\textpm 50 K. Temperature evolution of Raman spectra indicates that there may be another structural transition at higher temperatures, around 1300 K. Raman spectroscopy results are consistent with other characterization data (x-ray diffraction, reflection high energy electron diffraction, terahertz spectroscopy).