R&D: 3-Layer Exchange Coupled Composite Media for HAMR

IEEE Transactions on Magnetics has published an article written by Yijia Liu, School of Physics and Astronomy, University of Minnesota of Technology, Minneapolis, MN, USA, and R.H. Victora, School of Physics and Astronomy, University of Minnesota of Technology, Minneapolis, MN, USA, and Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA.

Abstract: “A novel three-layer thermally exchange coupled composite (3ly-ECC) media is proposed to mitigate 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 BER by ∼85% in the absence of intergranular exchange, compared to 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 reveals 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 to 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 of HAMR device.“