R&D: Adjacent Track Interference in HAMR

Journal of the Magnetics Society of Japan has published an article written by T. Kobayashi, Graduate School of Engineering, Mie Univ., Japan, Y. Nakatani, Graduate School of Informatics and Engineering, Univ. of Electro-Communications, Japan, and Y. Fujiwara, Graduate School of Engineering, Mie Univ., Japan.

Abstract: “We examine here the adjacent track interference (ATI) problem that arises when writing in an adjacent track for heat-assisted magnetic recording combined with shingled magnetic recording (shingled HAMR). For ATI, the bit error rate is a function of readout track width. We calculate the bit error rate and the minimum normalized readout field for various readout track widths. The factors affecting ATI are grain temperature and grain volume. We compare ATI and writing sensitivity for all combinations of 2 and 4 Tbpsi, and 6 and 9 grains/bit under the conditions of constant grain volume and constant grain height. For constant grain volume, 4 Tbpsi shingled HAMR is less advantageous than 2 Tbpsi shingled HAMR in terms of ATI due to the higher grain temperature caused by the smaller grain pitch. The grain number per bit must be lower and the grain height must be greater to be able to improve ATI for 4 Tbpsi shingled HAMR. We show there to be a loss of writing sensitivity for 4 Tbpsi shingled HAMR due to a statistical factor caused by the lower grain number per bit and the higher thermal stability factor resulting from the larger grain volume.“