Multiple Spin Injection Into Coupled Field Generation Layers for Low Current Operation of MAMR Heads

Microwave-assisted magnetic recording (MAMR) is a promising technique for improving the recording density of hard disk drives (HDDs). We propose a spin-torque oscillator (STO) structure with two field generation layers (FGLs) and two spin-injection layers (SILs) for microwave generation. By using a macrospin model and micromagnetic simulations, we numerically demonstrate the low current operation of the STO. The nearly antiparallel oscillations of the FGLs, which make suitable microwave distribution for MAMR, are stabilized by slight modulation of the in-plane phases of the FGLs and synchronization of the SILs. The enlarged spacing between the FGLs enhances the microwave amplitude at the media plane. These results indicate that, by using the dual-SIL dual-FGL STO, write heads for MAMR can operate using little energy to achieve high recording density.