Post-Annealing Effect on Magnetic, Electrical, and Adhesive Properties of FePdB Thin Films

FePdB was sputtered on glass substrate at room temperature (RT) to thicknesses of 1000 Å, 2000 Å, 3000 Å, 4000 Å and 5000 Å with post-annealing treatment at 150 °C and 250 °C. X-ray diffraction (XRD) revealed that each FePdB thin-film yielded a significant FePd (111) crystalline peak with a 2θ of 41.17°. As the film thickness increased with the annealing temperature, the FePd (111) crystallinity became stronger. The FePd (111) texture induced the magneto crystalline anisotropy, which reduced electrical resistivity (ρ) and was associated with increased low-frequency alternative-current magnetic susceptibility (χac). The value of χac increased with the thickness and post-annealing temperature due to magneto crystalline anisotropy. The maximum value of χac was 4.2, which was obtained at a thickness of 5000 Å with post-annealing 250 °C at the optimal resonance frequency (f res) of 250 Hz, and corresponded to the highest spin sensitivity. The resistivity (ρ) fell as the FePdB thickness and post-annealing temperature increased, because the grain boundaries and the thin-film surface scattered the electrons. The 5000 Å-thick FePdB thin film that was post-annealed at 250 °C had the lowest ρ, which was approximately 246 μΩ · cm. Adhesion critically affects the surface energy of a film. The surface energies of the as-deposited FePdB films herein exceeded those of the post-annealed films, revealing that the adhesion of as-deposited FePdB films was stronger than that of post-annealed films, owing to different degrees of crystallinity. According to the χac and ρ values of the films, the 5000 Å-thick FePdB thin film that was post-annealed at 250 °C was the best suited to magnetic and electric component applications. The as-deposited 1000 Å-thick FePdB had the highest surface energy and adhesion, and can be combined with other layers in various applications.