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

Abstract

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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> s) that excite high-frequency magnetic fields were derived for various Gilbert damping factors (αs) and saturation magnetization (4πM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) in the field generating layer. Second, J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> s were derived for various isolated STO structures. The effect of the material characteristics on J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> was also investigated.