  High storage density and high data rate are two of the most desired
properties of modern hard disk drives. Heat-assisted magnetic recording (HAMR)
is believed to achieve both. Recording media, consisting of exchange coupled
grains with a high and a low $T_{\mathrm{C}}$ part, were shown to have low DC
noise, but increased AC noise, compared to hard magnetic single phase grains,
like FePt [1]. In this work we extensively investigate the influence of an FeRh
interlayer on the magnetic noise in exchange coupled grains. We find an optimal
grain design that reduces the jitter in down-track direction by up to 30 % and
in off-track direction by up to 50 %, depending on the head velocity, compared
to the same structures without FeRh. Further, the mechanisms causing this
jitter reduction are demonstrated. Additionally, we show that for ultrashort
heat pulses and low write temperatures the switching time distribution of the
analyzed grain structure is reduced by a factor of four, compared to the same
structure without FeRh layer. This feature could be interesting for HAMR with a
pulsed laser spot and could resume the discussion about this HAMR technique.
