Improving the signal-to-noise ratio for heat-assisted magnetic recording by optimizing a high/low Tc bilayer structure

We optimize the recording medium for heat-assisted magnetic recording by using a high/low Tc bilayer structure to reduce AC and DC noise. Compared to a former work, small Gilbert damping alpha=0.02 is considered for the FePt-like hard magnetic material. Atomistic simulations are performed for a cylindrical recording grain with diameter d=5nm and height h=8nm. Different soft magnetic material compositions are tested, and the amount of hard and soft magnetic material is optimized. The results show that for a soft magnetic material with alpha SM=0.1 and Jij,SM=7.72x10-21J/link, a composition with 50% hard and 50% soft magnetic material leads to the best results. Additionally, we analyze how much areal density can be improved by using the optimized bilayer structure compared to the pure hard magnetic recording material. It turns out that the optimized bilayer design allows an areal density that is 1Tb/in.2 higher than that of the pure hard magnetic material while obtaining the same signal-to-noise ratio.