Effect of Effective Field Distribution on Recording Performance in Microwave Assisted Magnetic Recording

We investigated the effect of effective field distribution on the recording performance in microwave-assisted magnetic recording (MAMR) through calculations. We calculated the effective field distribution and the recording characteristics for different media that had similar grain sizes, but different anisotropy fields (Hk). We found that the effective field gradient near the trailing edge of the main pole was drastically enhanced because of the localized AC-field (Hac) near the spin-torque oscillator (STO) and the field angle distribution of writer, which affects on assist effect on the reducing the switching field (Hsw) of the media with applying the (Hac). It was also clarified that the SNR at high linear density drastically increased as the (Hk) of the media increased. This is because the effective field gradient at the (Hsw) of media increases as (Hk) of media is increased. Furthermore, SNR can be increased by reducing the grain size of media with high (Hk). Therefore, increasing both the (Hk) of media and the (Hac) of the STO is effective for achieving high areal density from view point of utilizing small grain media as well as high field gradient.