Characterization of c-oriented BaFe12O19 films synthesized by ion beam deposition on Al2O3 (102) substrate

Abstract

In this work, textured c-oriented BaFe12O19 films were synthesized by ion-beam deposition on Al2O3 (102) substrates. The texturing of the films was achieved by special deposition regime, based on the periodic interruptions of the process. These interruptions promoted spontaneous formation of (00 l) nuclei on the surface. After resumption of deposition these surface nuclei covered with next portion of the material. During the next break in deposition, nuclei (00 l) are again formed on the surface. By the end of the process, the entire volume of the film is filled with such nuclei; therefore, after crystallization annealing, the films become textured. It was found that the duration of pauses in the deposition affects the microstructure of hexaferrite and the optimal value of the time interval is proposed. To further increase the texture degree of the films, it was proposed to introduce the operation of preliminary annealing into the synthesis process. It was established that with an increase in the pre-annealing temperature from 300 to 900°C, the saturation magnetization, residual magnetization, and coercive force change nonmonotonically with a maximum at 500 °C. The microstructure of the film surface was also affected by the pre-annealing regime. An explanation for these effects is proposed and associated with the formation of the α-Fe2O3 (102) interlayer and the diffusion of aluminum from substrate to the film. The X-ray diffraction patterns of the obtained films do not differ, and all reflexes of hexaferrite are represented by the {00 l} set.