Raman study of BaFe12O19 thin films

We report on Raman spectra of BaFe12O19 thin films. These thin films have been deposited by injection chemical vapor deposition on three different substrates: Al2O3 (001), Gd3Ga5O12 (111), and Si (100). The observed Raman-active vibrations of the films are compared with recently published Raman spectra from bulk compounds. Surprisingly, we observed nearly the same spectra for all the films, although x-ray diffraction indicates polycrystalline (Si), textured (Gd3Ga5O12), and epitaxial (Al2O3) structure. We interpret these results by supposing the coexistence of well oriented regions and randomly oriented microcrystallites, which are not detectable by x-ray diffraction. Furthermore, by Raman spectroscopy we identified an additional phase for the films deposited on Al2O3 which has not been observed by x-ray diffraction either.