Noise Mitigation in Granular and Bit-Patterned Media for HAMR

Feasibility of heat assisted magnetic recording for granular and bit-patterned media (BPM) is evaluated in the context of various noises. Using micromagnetic simulation of renormalized media cells, we predict that the jitter is only 0.58 nm at a head speed of 10 m/s for the bilayer structure of FeRh/FePt when the grain size is 3.2 nm, validating the possibility of 6 Tb/in². We propose a new structure FePt/Cr/X/FePt that uses a Cr layer to produce an antiferromagnetic coupling that mimics the behavior of FeRh/FePt. We also confirmed the consistency of our renormalization approach for cell sizes from 1.0 to 1.5 nm. The temperature distribution is analyzed for BPM for areal densities of 2.2-5 Tb/in². We have predicted the maximum tolerable on-track bit temperatures at different areal densities and filling factors and substantiate the feasibility of BPM at 5 Tb/in² by observing successful and deterministic switching under a realistic temperature distribution.