Raman study of BaFe12O19 thin films

We report on Raman spectra of BaFe12O19 thin films. These thin films have b een deposited by injection chemical vapor deposition on three different sub strates: Al2O3 (001), Gd3Ga5O12 (111), and Si (100). The observed Raman-act ive vibrations of the films are compared with recently published Raman spec tra 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 thes e results by supposing the coexistence of well oriented regions and randoml y 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 diffracti on either. (C) 1998 American Institute of Physics, [S0003-6951(98)03635-3].