Systematic parameterization of heat-assisted magnetic recording switching probabilities and the consequences for the resulting SNR

Abstract

The signal-to-noise ratio (SNR) of a bit series written with heat-assisted magnetic recording on granular media depends on a large number of different parameters. The choice of material properties is essential for the obtained switching probabilities of single grains and, therefore, for the written bits' quality in terms of SNR. Studies where the effects of different material compositions on transition jitter and the switching probability are evaluated were done, but it is not obvious, how significant those improvements will finally change the received SNR. To investigate that influence, we developed an analytical model of the switching probability phase diagram, which contains independent parameters for, inter alia, transition width, switching probability, and curvature. Different values lead to corresponding bit patterns on granular media, where a reader model detects the resulting signal, which is finally converted to a parameter dependent SNR value. For grain diameters between 4 and 8 nm, we show an increase of ∼ 10 dB for bit lengths between 4 and 12 nm, an increase of ∼ 9 dB for maximum switching probabilities between 0.64 and 1.00, a decrease of ∼ 5 dB for down-track-jitter parameters between 0 and 4 nm, a decrease of 1-3 dB for off-track-jitter parameters between 0 and 50 K, and an increase of ∼ 0.5 dB for the reduced bit curvature. Those results are furthermore compared to the theoretical formulas for the SNR. We obtain a good agreement, even though we show slight deviations.