17:00 〜 17:15
▼ [14p-2J-12] Microstructure design of Spin-Torque-Oscillator for microwave assisted magnetic recording applications using micromagnetic simulation
キーワード：Spin-Torque-Oscillator,micromagnetic simulation,spin polarization
Microwave assisted magnetic recording (MAMR) is considered as one of good candidates for next generation higher areal density magnetic recording technology. For MAMR writer, mag-flip spin-torque-oscillator (STO) consisting of out -of-plane magnetized spin injecting layer (SIL) and in-plane magnetized field generating layer (FGL) is required. Mirowave frequency of above 20 GHz is required to be oscilated with a current density below 1.0×108 A/cm2 . However, this has not been realized experimentally. In this work, we employed micromagnetic simulations to study the effect of spin polarization (β) and saturation magnetization (µ0Ms) of SIL and FGL on the oscillation behavior of a mag-flip STO device.
Micromagnetic simulation results showed that frequency peaks shifts to smaller values with increasing µ0Ms of the FGL layer, and no oscillation was found for µ0Ms=2.3 T. In addition, multi-mode oscillation and spin waves were observed for µ0Ms= 1.7 and 1.9 T. However, by the reduction of the size of STO device from 60×60 nm2 to 30×30 nm2, a uniform oscillation was observed due to the reduction of the demagnetization field. The frequency and the oscillation angle are increased with spin polarization of FGL. Micromagnetic simulations showed that the increase of µ0Ms of SIL can hinder magnetization switching of FGL and is beneficial to induce out-of-plane oscillation in the FGL. In order to study the effect of spin polarization of SIL to the oscilation behavior of FGL, simulation was carried out by solving spin diffusion equations in parallel to LLG equation to consider the effect of spin accumulation at the interfaces. The frequency peak increases from 21 GHz to 25 GHz by increasing the spin polarization of SIL from 0.5 to 0.85, for the current density of just 1.0×108 A/cm2. Higher spin polarization in SIL layer leads to a smaller threshold for the current density to oscilate the FGL layer.
Micromagnetic simulation results showed that frequency peaks shifts to smaller values with increasing µ0Ms of the FGL layer, and no oscillation was found for µ0Ms=2.3 T. In addition, multi-mode oscillation and spin waves were observed for µ0Ms= 1.7 and 1.9 T. However, by the reduction of the size of STO device from 60×60 nm2 to 30×30 nm2, a uniform oscillation was observed due to the reduction of the demagnetization field. The frequency and the oscillation angle are increased with spin polarization of FGL. Micromagnetic simulations showed that the increase of µ0Ms of SIL can hinder magnetization switching of FGL and is beneficial to induce out-of-plane oscillation in the FGL. In order to study the effect of spin polarization of SIL to the oscilation behavior of FGL, simulation was carried out by solving spin diffusion equations in parallel to LLG equation to consider the effect of spin accumulation at the interfaces. The frequency peak increases from 21 GHz to 25 GHz by increasing the spin polarization of SIL from 0.5 to 0.85, for the current density of just 1.0×108 A/cm2. Higher spin polarization in SIL layer leads to a smaller threshold for the current density to oscilate the FGL layer.