This study investigated Co₄₀Fe₄₀W₂₀ single-layer thin films according to their corresponding structure, grain size, contact angle, and surface energy characteristics. Co₄₀Fe₄₀W₂₀ alloy thin films of different thicknesses, ranging from 10 to 50 nm, were sputtered on Si(100) substrates by DC magnetron sputtering. The thin films were annealed under three conditions: as-deposited, 250 °C, and 350 °C temperatures, respectively. The Scherrer equation was applied to calculate the grain size of Co₄₀Fe₄₀W₂₀ thin films. The results show that the grain size of CoFe(110) increased simultaneously with the increase of post-annealing temperature, suggesting that the crystallinity of Co₄₀Fe₄₀W₂₀ thin films increased with the post-annealing temperature. Moreover, the contact angles of all Co₄₀Fe₄₀W₂₀ thin films were all less than 90°, suggesting that Co₄₀Fe₄₀W₂₀ thin films show changes in the direction of higher hydrophilicity. However, we found that their contact angles decreased as the grain size of CoFe increased. Finally, the Young equation was applied to calculate the surface energy of Co₄₀Fe₄₀W₂₀ thin films. After post-annealing, the surface energy of Co₄₀Fe₄₀W₂₀ thin films increased with the rising post-annealing temperature. This is the highest value of surface energy observed for 350 °C. In addition, the surface energy increased as the contact angle of Co₄₀Fe₄₀W₂₀ thin films decreased. The high surface energy means stronger adhesion, allowing the formation of multilayer thin films with magnetic tunneling junctions (MTJs). The sheet resistance of the as-deposited and thinner CoFeW films is larger than annealed and thicker CoFeW films. When the thickness is from 10 nm to 50 nm, the hardness and Young’s modulus of the CoFeW film also show a saturation trend.

In this study, a 10–50 nm Co₃₂Fe₃₀W₃₈ alloy thin film sputtered on glass substrates was annealed at different temperatures for 1 h including room temperature (RT), 300, 350, and 400 °C. The structure, magnetic properties, surface energy, and optical properties of the Co₃₂Fe₃₀W₃₈ alloy were studied. X-ray diffraction (XRD) patterns of the as-deposited Co₃₂Fe₃₀W₃₈ thin films showed the amorphous structure. The apparent body-centered cubic (BCC) CoFe (110) structure was exhibited after 300 °C annealing for 1 h. The 300 °C annealed Co₃₂Fe₃₀W₃₈ thin film showed the highest CoFe (110) peak compared with other temperatures. Furthermore, the thicker the Co₃₂Fe₃₀W₃₈ thin film, the higher the CoFe (110) peak. The CoFe (110) peak revealed magneto-crystalline anisotropy, which was related to the strong low-frequency alternative-current magnetic susceptibility (χ_ac) and induced an increasing trend of saturation magnetization (M_s) as the thickness (t_f) increased. Due to the thermal disturbance, the χ_ac and M_s for the 350 and 400 °C annealed Co₃₂Fe₃₀W₃₈ thin film decreased. The contact angles of the Co₃₂Fe₃₀W₃₈ thin films were less than 90°. For all temperatures, the surface energy increased when the film thickness increased from 10 to 50 nm. In addition, the surface energies for annealed samples were comparatively higher than the as-deposited samples. The higher surface energy of 28 mJ/mm² was obtained for the 50 nm Co₃₂Fe₃₀W₃₈ thin film annealed at 300 °C. The transmittance percentage (%) of the as-deposited Co₃₂Fe₃₀W₃₈ film was higher than other annealed conditions. This result contributed to the fact that higher crystallization, due to perfect band structures, may inhibit the transmission of photon signals through the film, resulting in low transmittance and high absorption.

Co₄₀Fe₄₀W₂₀ monolayers of different thicknesses were deposited on Si(100) substrates by DC magnetron sputtering, with Co₄₀Fe₄₀W₂₀ thicknesses from 10 to 50 nm. Co₄₀Fe₄₀W₂₀ thin films were annealed at three conditions (as-deposited, 250 °C, and 350 °C) for 1 h. The structural and magnetic properties were then examined by X-ray diffraction (XRD), low-frequency alternative-current magnetic susceptibility (χ_ac), and an alternating-gradient magnetometer (AGM). The XRD results showed that the CoFe (110) peak was located at 2θ = 44.6°, but the metal oxide peaks appeared at 2θ = 38.3, 47.6, 54.5, and 56.3°, corresponding to Fe₂O₃ (320), WO₃ (002), Co₂O₃ (422), and Co₂O₃ (511), respectively. The saturation magnetization (Ms) was calculated from the slope of the magnetization (M) versus the CoFeW thickness. The Ms values calculated in this manner were 648, 876, 874, and 801 emu/cm³ at the as-deposited condition and post-annealing conditions at 250, 350, and 400 °C, respectively. The maximum M_S was about 874 emu/cm³ at a thickness of 50 nm following annealing at 350 °C. It indicated that the M_S and the χ_ac values rose as the CoFeW thin films’ thickness increased. Owing to the thermal disturbance, the M_S and χ_ac values of CoFeW thin films after annealing at 350 °C were comparatively higher than at other annealing temperatures. More importantly, the Co₄₀Fe₄₀W₂₀ films exhibited a good thermal stability. Therefore, replacing the magnetic layer with a CoFeW film improves thermal stability and is beneficial for electrode and strain gauge applications.