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.
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