Effect of Yttrium Addition on Structure and Magnetic Properties of Co(60)Fe(20)Y(20) Thin Films

In this paper, a Co(60)Fe(20)Y(20) film was sputtered onto Si (100) substrates with thicknesses ranging from 10 to 50 nm under four conditions to investigate the structure, magnetic properties, and surface energy. Under four conditions, the crystal structure of the CoFeY films was found to be amorphous by an X-ray diffraction analyzer (XRD), suggesting that yttrium (Y) added into CoFe films and can be refined in grain size and insufficient annealing temperatures do not induce enough thermal driving force to support grain growth. The saturation magnetization (M(S)) and low-frequency alternate-current magnetic susceptibility (χ(ac)) increased with the increase of the thicknesses and annealing temperatures, indicating the thickness effect and Y can be refined grain size and improved ferromagnetic spin exchange coupling. The highest Ms and χ(ac) values of the Co(60)Fe(20)Y(20) films were 883 emu/cm(3) and 0.26 when the annealed temperature was 300 °C and the thickness was 50 nm. The optimal resonance frequency (f(res)) was 50 Hz with the maximum χ(ac) value, indicating it could be used at a low frequency range. Moreover, the surface energy increased with the increase of the thickness and annealing temperature. The maximum surface energy of the annealed 300 °C film was 30.02 mJ/mm(2) at 50 nm. Based on the magnetic and surface energy results, the optimal thickness was 50 nm annealed at 300 °C, which has the highest Ms, χ(ac), and a strong adhesion, which can be as a free or pinned layer that could be combined with the magnetic tunneling layer and applied in magnetic fields.