R&D: Goldak’s Double Ellipsoidal Thermal Profile Model of Transition Jitter and Signal-to-noise Ratio for HAMR

Journal of Applied Physics has published an article written by Chavakon Jongjaihan, Pirat Khunkitti, and Arkom Kaewrawang, Department of Electrical Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen, Thailand.

Abstract: “The characteristics of the magnetic footprints for heat-assisted magnetic recording (HAMR) are determined by the thermal profile. Thermal profile models are one of the factors that affect the signal-to-noise ratio (SNR) and the transition jitter of the medium. These factors influence the increase in areal density. This work uses a new thermal profile model, Goldak’s double ellipsoidal heat source to simulate a moving heat spot. Down-track thermal gradient (DTG) and cross-track thermal gradient (CTG) from the thermal profile model are defined to correspond to the head velocity. DTG and CTG are among the parameters that determine linear density and track density. They also play an important role in the transition quality for HAMR. Therefore, the effect of the thermal profile on transition jitter and SNR is investigated. Micromagnetic simulation was used for the magnetic recording process. L 1 0-FePt was used as the magnetic material of the medium. The average grain size was 3.5 nm and the grain size distribution was 0.09 nm. The results indicate that the appropriate geometrical scaling with the minimum average transition jitter is 1.180 nm at a full width at half maximum (FWHM) of 60 nm, a ratio of read width (RW) to FWHM (RW/FWHM) of 25% and a DTG of 5.2 K/nm. In addition, the maximum SNR is 8.558 dB at a FWHM of 60 nm, RW/FWHM of 30%, and a DTG of 5.2 K/nm.“