Tunable cut-off frequency by in-plane uniaxial anisotropy in (Fe_66.9Co_33.1)_86.8Sm_13.2 films

(Fe_66.9Co_33.1)_86.8Sm_13.2 (FeCoSm) thin films with thickness from 110 to 330 nm are fabricated on silicon (1 1 1) substrates by magnetron co-sputtering under ambient condition. The as-deposited FeCoSm thin film is amorphous when the thickness is less than 150 nm. When the thickness increases further, the film becomes partially crystallized. The maximum in-plane uniaxial anisotropy field is up to 1200 Oe. After the films are heat treated in vacuum with a magnetic field, the in-plane uniaxial anisotropy field decreases with an increase in annealing temperature and becomes zero after annealing at 500 °C. The dynamic magnetic properties of the FeCoSm films are also investigated in the range 0.1–9 GHz. Based on the one-terminal micro-strip transmission-line perturbation method and an analysis by the Landau–Lifshitz equation, the anisotropy field and the resonance frequency of the FeCoSm_films are in the range 50–1200 Oe and 1.8–12.1 GHz, respectively. The anisotropy field and resonance frequency of the film can be controlled by varying the film thickness or annealing temperature, this means that FeCoSm films have great potential in high-frequency applications.