  The dynamic process of assisted magnetic switchins has been simulated to
investigate the associated physics. The model uses a Voronoi construction to
determine the physical structure of the nano granular thin film recording
media; and the Landau-Lifshitz-Bloch (LLB) equation is solved to evolve the
magnetic system in time. The reduction of the magnetization is determined over
a range of peak system temperatures and for a number of anisotropy values. The
results show that the HAMR process is not simply magnetization reversal over a
thermally reduced energy barrier. To achieve full magnetization reversal (for
all anisotropies investigated) an applied field strength of at least 6kOe is
required and the peak system temperature must reach at least the Curie point
(Tc). When heated to Tc the magnetization associated with each grain is
destroyed, which invokes the non-precessional linear reversal mode. Reversing
the magnetization through this linear reversal mode is favourable, as the
reversal time is two orders of magnitude smaller than that associated with
precession. Under these conditions, as the temperature decreases to ambient,
the magnetization recovers in the direction of the applied field, completing
the reversal process. Also the model produces results which are consistent with
the concept of thermal writability; when heating the media to Tc, the smaller
grains require a larger field strength to reverse the magnetization.
