  The linear reversal mechanism in FePt grains ranging from 2.316 nm to 5.404
nm has been simulated using atomistic spin dynamics, parametrized from
ab-initio calculations. The Curie temperature and the critical temperature
(T*), at which the linear reversal mechanism occurs, are observed to decrease
with system size whilst the temperature window T* < T < TC increases. The
reversal paths close to the Curie temperature have been calculated, showing
that for decreasing system size the reversal path becomes more elliptic at
lower temperatures, consistent with the decrease in the Curie temperature
arising from finite size effects. Calculations of the minimum pulse duration
show faster switching in small grains and is qualitatively described by the
Landau-Lifshitz-Bloch equation with finite size atomistic parameterization,
which suggests that multiscale modeling of FePt down to a grain size of ~ 3.5
nm is possible.
