High frequency out-of-plane oscillation with large cone angle in mag-flip spin torque oscillators for microwave assisted magnetic recording

We investigated spin torque induced magnetization dynamics in the mag-flip spin torque oscillators (STOs) of diameters D from 29 to 96 nm comprising of an in-plane magnetized field generation layer (FGL) Fe₆₇Co₃₃ (7 nm) with high saturation magnetization, μ₀M_s ∼ 2.3 T, and perpendicular FePt(10 nm)/Co₂FeGa_0.5Ge_0.5(3 nm) highly spin polarized spin injection layers. Out-of-plane high frequency, f ∼ 21-26 GHz, spin torque induced oscillation with a large cone angle in FGL was observed under nearly perpendicular external magnetic field μ₀H_ext of 1.1 T for the pillar D of 29 and 42 nm. Our micromagnetic simulation results indicated that ac magnetic fields of about 0.15 to 0.2 T are obtainable from the STOs having the same stacking structure and size as the experiment, which is large enough for the applications to microwave assisted magnetic recording technology.