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

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 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 were present for Si substrate. Using a magneto-optical Kerr effect magnetometer, it was found that, for the FeSiB films, the anisotropy held (H
_k
) increased slowly as the pressure increased, while for the FeGaSiB films, the saturation held (H
_s
) ≈ 4000 A/m for all pressures. For both the film sets, the coercive held (H
_c
) was less than 800 A/m. The magnetostriction constants (λ
_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 λ
_s
= 11.4 ppm, at the lowest pressure 4 μbar. Thus, it was determined that the addition of Ga atoms reduced the intrinsic stress within the films, while maintaining the amorphous morphology.