R&D: Error Factors for Writability in Heat-Assisted Magnetic Recording (HAMR)

Journal of the Magnetics Society of Japan has published an article written by T. Kobayashi, Graduate School of Engineering, Mie Univ.,1577 Kurimamachiya-cho, Tsu 514-8507, Japan, I. Tagawa, Electrical and Electronic Engineering, Tohoku Institute of Technology, 35-1 Yagiyama-Kasumicho, Sendai 982-8577, Japan, and Y. Nakatani, Graduate School of Informatics and Engineering, Univ. of Electro-Communications, 1-5-1 Chofugaoka, Chofu 182-8585, Japan.

Abstract: “We analyze the error factors, namely erasure-before-write (EBW), erasure-after-write (EAW), Curie temperature 𝑇_c variation, write-error (WE), statistical factor, and anisotropy constant, for writability in heat-assisted magnetic recording (HAMR) employing a stochastic calculation. We separate the bit error rate bER for each grain column in 2 bits of data. We focus on the mean magnetization reversal numbers per unit time 𝑁_– and 𝑁₊ for the magnetization reversal in the recording direction and in the opposite direction to the recording direction, respectively, and the medium writing time 𝜏_med, which is a time where the 𝑁_– value is large during writing. EBW and EAW are related to the 𝑇_c variation through the 𝑁_– value. WE can be improved by increasing the 𝑁_– and 𝜏_med values and reducing the 𝑁₊ value. The increase in the grain number per bit is advantageous for reducing the bER value in terms of the statistical factor. The 𝜏_med value is increased and the 𝑁₊ value is reduced by reducing the anisotropy constant. However, EAW increases due to the long 𝜏_med value. Since the influence of EAW is large in HAMR, we may not reduce the anisotropy constant in HAMR as is possible in heated-dot magnetic recording.“