Fabrication and characterization of magnetostrictive amorphous FeGaSiB thin films

Abstract

In this work, amorphous FeSiB and FeGaSiB thin films have been fabricated on silicon substrates using a co-sputtering-evaporation deposition technique. The effect of adding gallium into FeSiB (Metglas) thin films on the structure, magnetic properties and magnetostriction have been studied. From x-ray diffraction (XRD), all the films were amorphous and the observed peaks were for the Si substrate. X-ray Photoelectron Spectroscopy (XPS) measurements were carried out to determine the film's composition, which was found to be Fe 83 Ga 11 Si 5.2 B 0.8. Atomic force microscopy (AFM) images were taken to measure the film thickness along with studying the surface topography. It was found that the film surface had an average roughness of 0.461 nm. For both FeSiB and FeGaSiB thin films, the effect of the thickness of the films on the magnetic properties and magnetostriction were investigated. The results showed that adding Ga into the FeSiB films changed the magnetic properties by reducing the saturation induction along with changing the magnetic anisotropy from uniaxial to isotropic. For the FeGaSiB films, the coercive field decreased and the saturation field (H s) increased with film thickness. The magnetostriction constants of the FeGaSiB films were all larger than the FeSiB films for thicknesses greater than 40nm.

Influence of Ga evaporation rate on the magnetic properties of Amorphous FeGaSiB thin films

“…While changing the sputtering gas pressure at fixed Ga rate (0.2 a.u), for 50nm FeGaSiB film [19] did not affect the morphology of the films, but the magnetostriction constant decreased with increasing Ar pressure. This work extends our previous study, by using the optimised fabrication parameters (sputtering power (20W) and pressure (4 µbar)) determined from our previous papers [18,19] and increasing the Ga concentration by increasing the Ga rate to investigate how a larger amount of Ga in the ratio FeSiB:Ga in these films, effects the morphology, magnetic properties, and magnetostriction constant (s) of FeGaSiB thin films.…”

“…Thus for the film at Ga 7%, D ≈ 0.3, so has weak uniaxial anisotropy, while a stronger uniaxial anisotropy is present in the film at Ga 8% where D ≈ 0.83 (see Figure 4). FeSiB film grown with the same fabrication parameters and Hk ≈ 2300 A/m [18,19], the FeGaSiB films all have a higher anisotropy field. The anisotropy energy depends on the anisotropy constant, which is given by eqn (2).…”

“…Thus, the 14% Ga film, has less pinning compared to the 7% Ga film, so a smaller Mr/Ms along the hard axis, this leads to the observation of strong uniaxial anisotropy observed in Figure 3 inset, but as it has a smaller Ms compared to the 7% Ga film but the same Hk, so the anisotropy constant, hence energy is smaller compared to the 7% Ga film. [18,19] of Hc ≈ 800 A/m. This means that the Ga addition has reduced the coercive field, probably due to reduced domain wall pinning in the higher concentration films, as suggested by the Mr/Ms data.…”

“…Our previous work [18] on FeSiB and FeGaSiB thin films grown on Si substrate using a cosputtering-evaporation technique determined how film thickness and sputtering pressure [19] affected the structural and magnetic properties. These results showed that adding Ga to amorphous FeSiB films in the thickness range 24-100 nm did not affect the morphology of the films, but the magnetic properties and magnetostriction constants were changed.…”

Designing ferrite impregnated epoxy actuators for impact damage detection in carbon fibre reinforced composites

“…Magnetostrictive materials experience a change in magnetisation in response to an applied strain [6]. Magnetostrictive materials can be considered for BVID detection [7][8][9][10]. Previous studies investigated magnetostrictive wires and ribbons either embedded inside the composite or mounted on the composite surface with specific lay-up patterns.…”