Effect of Transmitted Spin from Head Poles in MAMR

In microwave assisted magnetic recording (MAMR), it is still a challenge to obtain stable oscillation of magnetization in the spin torque oscillator (STO). In this paper we point out that one possible problem in practical MAMR heads is oscillation disturbance by transmitted spins from the head poles, i.e. the main pole and trailing shield, and also discuss the requirements for good STO oscillation. We propose structure design candidates with a short spin-diffusion length material and with a negative spin-polarization material to obtain a larger microwave assist field generated from the STO using micromagnetics simulation.