  The signal-to-noise ratio (SNR) of a bit series written with heat-assisted
magnetic recording (HAMR) 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
8nm, we show an increase of ~10dB for bit lengths between 4 and 12nm, an
increase of ~9dB for maximum switching probabilities between 0.64 and 1.00, a
decrease of ~5dB for down-track-jitter parameters between 0 and 4nm and an
increase of ~1dB for 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.
