# Improving the Signal-to-noise Ratio for Heat-Assisted Magnetic Recording by Optimizing a High/Low Tc bilayer structure

## TL;DR

This paper presents an optimized high/low Tc bilayer structure for heat-assisted magnetic recording, significantly reducing noise and increasing areal density by 1 Tb/in² while maintaining the same SNR.

## Contribution

It introduces a novel bilayer design with specific material compositions that improves recording density and noise performance over traditional pure hard magnetic media.

## Key findings

- Optimized bilayer structure achieves 1 Tb/in² higher areal density.
- Soft magnetic material with α=0.1 and J=7.72×10⁻²¹ J/link is optimal.
- The design maintains the same SNR as pure hard magnetic media.

## Abstract

We optimize the recording medium for heat-assisted magnetic recording by using a high/low $T_{\mathrm{c}}$ 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 $d=5\,$nm and height $h=8\,$nm. 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 $\alpha_{\mathrm{SM}}=0.1$ and $J_{ij,\mathrm{SM}}=7.72\times 10^{-21}\,$J/link a composition with $50\%$ hard and $50\%$ soft magnetic material leads to the best results. Additionally, we analyse how much the 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 $1\,$Tb/in$^2$ higher than that of the pure hard magnetic material while obtaining the same SNR.