R&D: Information Stability in 3D HAMR

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

Abstract: “The anisotropy constant ratio K_u / K_bulk necessary for information stability in three-dimensional heat-assisted magnetic recording (3D HAMR) of 2 Tbpsi (total density of 4 Tbpsi) is evaluated by employing a bit error rate calculation using grain error probability. The minimum K_u / K_bulk value of a high Curie temperature (HC) layer is limited by the information stability in the HC layer while writing in a low Curie temperature (LC) layer, and a high K_u / K_bulk is necessary for the HC layer. The minimum K_u / K_bulk value of the LC layer is limited by the information stability in the LC layer for 10 years of archiving, and a high K_u / K_bulk is also necessary for the LC layer since the anisotropy constant of the LC layer is intrinsically low at the storage temperature due to its low Curie temperature. At 9 grains/bit, the K_u / K_bulk values required for 3D HAMR are 0.85 and 0.86 for the HC and LC layers, respectively, taking account of certain variations, namely, standard deviations of 2 % for the Curie temperature and 15 % for the grain size.“