Influence of Ar Pressure on the Magnetic Properties of Amorphous FeGaSiB Thin Films

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Magnetostrictive amorphous FeSiB and FeGaSiB thin films thickness 50 nm have been grown by the co-sputtering-evaporation technique with a range of Ar pressure (4– $8~\mu $ bar) to control the Ga percentage within the films and study their effect on the magnetic, structural, and magnetostriction properties. By X-ray diffraction, it was found that all the films had an amorphous structure and the only peaks were present for Si substrate. Using a magneto-optical Kerr effect magnetometer, it was found that, for the FeSiB films, the anisotropy field $(H_{k}$ ) increased slowly as the pressure increased, while for the FeGaSiB films, the saturation field $(H_{s}) \approx 4000$ A/m for all pressures. For both the film sets, the coercive field $(H_{c})$ was less than 800 A/m. The magnetostriction constants $(\lambda _{s})$ of the FeSiB thin films increased with increasing pressure. While for the FeGaSiB films, the magnetostriction constant decreased with increasing the sputtering gas pressure, with the maximum $\lambda _{s} = 11.4$ ppm, at the lowest pressure $4~\mu $ bar. Thus, it was determined that the addition of Ga atoms reduced the intrinsic stress within the films, while maintaining the amorphous morphology.