Three-Layer Exchange Coupled Composite Media for Heat-Assisted Magnetic Recording

A novel three-layer thermally exchange coupled composite (3ly-ECC) media is proposed to mitigate heat-assisted magnetic recording (HAMR)-related noise at reduced operating temperature, particularly transition noise. Leveraging the Zeeman effect and anisotropy field gradients to switch the writing layer and the middle layer, respectively, the proposed 3ly-ECCs effectively reduce transition jitter by ~15% and bit error rate (BER) by ~85% in the absence of intergranular exchange (IGE), compared with the 2ly-ECC with the same total thickness. The improvement in transition jitter is supported by an analytical analysis of the energy function using a simple spin model, which highlights the contribution of large anisotropy and small magnetization in the middle layer. However, it is noted that the 3ly-ECC is more susceptible to erasure-after-write (EAW) effect than 2ly-ECC. Calculations reveal that increasing the anisotropy of writing layer suppresses the EAW effect in 3ly-ECCs, yet adversely affects BER due to the loss of rapid switching. Overall, the proposed 3ly-ECC effectively balances fast switching and EAW to yield superior jitter and BER compared with the two-layer counterpart. The results suggest that future endeavors could focus on developing suitable high-Ku and low-Ms composite media to potentially improve the areal density (AD) of HAMR device.