  We developed a grain growth model that is based on the energy minimisation of
surfaces with respect to the volume energy and the grain's environment. We used
the well-known FePt L1$_\text{0}$ system to discover the physical factors that
drive the shape and size of FePt grains. It was found that the preferred growth
directions are along symmetry planes that are determined by the basic crystal
and driven by surface energy minimisation. The model developed here can be used
to predict a grain's growth and shape as a function of atomic number and
composition. This means that by tailoring a grain's surface and grain
boundaries the shape of the magnetic grains can be manipulated.
