Memory Erasure and Write Field Requirements in HAMR Using L \(1_\mathbf {o}\) -FePt Nanoparticles

The write field requirements in heat-assisted magnetic recording (HAMR) using FePt media are studied using an atomistic model. Langevin dynamics simulations of laser-induced thermal demagnetization and magnetization recovery are performed on a single L1
_o
-ordered FePt grain. We show that the minimum heat temperature for thermal overwrite of information is a cooling ratedependent temperature T
_o
, larger than the Curie temperature of the grains. If T
_o
is exceeded, memory effects can be neglected in HAMR since the characteristic pulse time is long compared with the mean first passage time of thermal demagnetization. The minimum write field H
_w
to attain sufficiently high thermoremanence M
_Z
= 0.9MS is then independent of the heating process. We study the variation of H
_w
with cooling rate, damping, field orientation, and grain size L, and explore the phase space of the parameters H, T, and L, also resulting in thermal stability of the recorded information during storage.