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

Magnetostrictive amorphous FeSiB and FeGaSiB thin films, thickness 50nm have been grown by the co-sputtering-evaporation technique with a range of Ar pressure (4 - 8 μbar) 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 present were for Si substrate. Using a magneto-optical Kerr effect (MOKE) magnetometer, it found that, for the FeSiB films, the anisotropy field (Hk) increased slowly as the pressure increased, while for the FeGaSiB films, the saturation field (Hs) ≈ 4000 A/m for all pressures. For both the film sets, the coercive field (Hc) was less than 800 A/m. The magnetostriction constants (λs) 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 λs = 11.4 ppm, at the lowest pressure 4μbar. Thus it was determined that the addition of Ga atoms reduced the intrinsic stress within the films, while maintaining the amorphous morphology.