Textured Growth of Strontium Ferrite Thin Films by Sputtering

Abstract

Study of M-type hexagonal ferrite films (BaFe 12 O 19 and SrFe 12 O 19 ) is drawing a lot of interest due to their potential applications. Ba ferrite films with perpendicular anisotropy have been studied due to their projected use in perpendicular recording media, magneto-optic recording media and in microwave/millimeter wave devices. The current interest in depositing these films with in plane anisotropy is for use in high density longitudinal recording media. There have been attempts to deposit these materials, mostly on crystalline substrates though without complete control over the orientation. We have for the first time deposited the sputtered strontium ferrite films and could vary the texture of the film to obtain both perpendicular and in plane anisotropy. It was found that the films prepared at lower rf power when annealed at temperatures ≥ 800 °C showed perpendicular anisotropy while the films prepared with higher rf power after similar annealing showed in plane anisotropy. These films had been prepared without substrate heating during sputter deposition and the as deposited films were X-ray amorphous and were nonmagnetic. However, these 'as deposited' films when annealed, showed different textures depending on the deposition conditions, as if these deposition conditions leave some signature in the films, which eventually decides the texture of these films. The microstructural studies showed that though the 'as deposited' films were X-ray amorphous, oriented microcrystallites form during deposition, which could be controlling the texture at the time of complete crystallization during annealing.