Micromagnetic Simulation of Spin-Torque Oscillator for Microwave-Assisted Magnetic Recording-Interaction between Write Head and STO and Optimum Injected Current

The spin-torque oscillator (STO) is the most important component in microwave-assisted magnetic recording (MAMR). To realize MAMR, a small injected STO current is mandatory, as are large amplitude and stable oscillations. In this paper, an isolated STO element (without the write head) and an STO integrated into a write head were analyzed using micromagnetic analysis. First, the integrated STO was used and the optimum injected currents ( J_opts ) that excite high-frequency magnetic fields were derived for various Gilbert damping factors (αs) and saturation magnetization (4πM_s) in the field generating layer. Second, J_opts were derived for various isolated STO structures. The effect of the material characteristics on J_opt was also investigated.