Abstract
In this paper, we present a methodology of segmented media stack design for microwave assisted magnetic recording. Through micro-magnetic modeling, it is demonstrated that an optimized media segmentation is able to yield high signal-to-noise ratio even with limited ac field power. With proper segmentation, the ac field power could be utilized more efficiently and this can alleviate the requirement for medium damping which has been previously considered a critical limitation. The micro-magnetic modeling also shows that with segmentation optimization, recording signal-to-noise ratio can have very little dependence on damping for different recording linear densities.
Highlights
With the grain size reduction, thin-film media segmented by the insertion of exchange breaking layers (EBLs) has been introduced into the conventional perpendicular magnetic recording (PMR) to improve the writability while maintaining high thermal stability.[1,2,3]
With micro-magnetic modeling, we demonstrate that with a proper segmentation stack design, microwave assisted magnetic recording (MAMR) could utilize the ac field power more efficiently and the signal-to-noise ratio (SNR) dependence on medium damping could be alleviated
While for the segmentation structure customized for MAMR, the recording SNR drops less than 3 dB even with the spin torque oscillator (STO) thickness reduces from 10 nm to 5 nm
Summary
With the grain size reduction, thin-film media segmented by the insertion of exchange breaking layers (EBLs) has been introduced into the conventional perpendicular magnetic recording (PMR) to improve the writability while maintaining high thermal stability.[1,2,3] in microwave assisted magnetic recording (MAMR), media segmentation stack design should have taken the vertical ac field distribution into consideration in order to achieve high area density capacity (ADC) gain.[4,5,6,7,8,9,10] In addition, damping has been considered as a primary limitation for MAMR at high ac frequencies.[4,5,6,11,12,13] And damping constant for high anisotropy media is usually large.[14] The reason that high medium damping limits MAMR performance is because of the energy loss during the switching process and this reinforces the importance of efficient ac field power utilization.
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