R&D: Effects of Dot-Position Dispersion of BPM, Thermal Distribution, and Head Field Gradient on Bit-Error for HAMR

Japanese Journal of Applied Physics has published an article written by Fumiko Akagi, and Naofumi Matsushima, Graduate School of Electrical Engineering and Electronic, Kogakuin University, Shinjuku, Tokyo 163-8677, Japan.

Abstract: “The effects of dot-position dispersion, thermal distribution, and the head field gradients in a cross-track direction on bit error rates for heat-assisted magnetic recording with bit-patterned media were studied using a micromagnetic simulation to achieve an areal recording density of 2.5Tb in⁻². A large dot-position dispersion in a cross-track direction causes on-track bit errors when the full width at half maximum (FWHM) of the thermal distribution was equal to or lower than 25nm. This is because the centers of the dots with errors were set to be unrecordable in the thermal attenuation area. When the FWHM was larger than 25nm, there were bit errors for all dot-position dispersion. The bit errors were caused by rewriting, which occurred during thermal fluctuations. The bit error of the down-track direction was more than that of the cross-track direction. Because of these results, the track width should be as narrow as possible.“