SNR and Areal Density Gain in MAMR With Segmented Media

In this paper, we present a micromagnetic modeling study on the switching property of segmented grains assisted by circularly polarized magnetic field at microwave frequencies and the actual recording process. This paper provides insightful understanding of the switching dependence on the Gilbert damping constant and the optimization for suppressing the impact of possible damping constant distribution. The recording processes with ac field generated by a spin torque oscillator on the media consisting of segmented grains are also investigated. In this microwave assisted magnetic recording (MAMR) process, the segmentation of the grains with exchange breaking layers enables the best utilization of the ac field. The MAMR simulations show significant signal-to-noise ratio (SNR) gain over today's perpendicular recording for medium for media with grain pitches
${<}{\rm 8}~{\rm nm}$
. Grain-pitch limited SNR performance can be achieved for medium grain pitches as small as 5 nm while achieving sufficient thermal stability simultaneously. At 4.5 nm grain pitch, MAMR shows significantly higher SNR than that predicted by corresponding HAMR simulations. It is concluded that MAMR should enable areal density capability of 4
${\rm Tb}/{\rm in}^{2}$
and beyond and its SNR performance is superior to HAMR at all densities.