Crystallization of amorphous precursor of ba-ferrite film: a real-time synchrotron x-ray scattering study

The crystallization of the amorphous precursor of a Ba-ferrite thin film was studied in real-time synchrotron x-ray scattering experiments. We found that a very thin (∼50 Å) epitaxial Fe₃O₄ sublayer was formed in the as-deposited amorphous precursor grown on sapphire (001). The nucleation of crystalline α-Fe₂O₃ phase from the amorphous precursor started at 300°C and continued at higher annealing temperatures. The mosaic distribution of the α-Fe₂O₃ grains was about 0.67° full-width at half-maximum (FWHM), relatively large compared to that of the Fe₃O₄ sublayer. The crystallization of the Ba-ferrite phase occurred at 600°C. The Fe₃O₄ sublayer was transformed from 600°C to extremely well-aligned (0.05° FWHM) α-Fe₂O₃ phase. It is noteworthy that the crystallization of the Ba-ferrite phase occurred during the transformation of the Fe₃O₄ sublayer to the well-aligned α-Fe₂O₃ grains. The Fe₂O₄ sublayer might play an important role in the crystallization of amorphous Ba-ferrite film.