Effect of crystallographic orientation on grain size distribution

The control of grain size statistics is essential in the manufacture of granular thin films used in high-density recording. In this article transmission electron microscope observations of perpendicular media are shown that indicate larger grain size dispersion than in typical longitudinal media. We explain this result by utilizing a simple Voronoi model that includes the crystallographic symmetry. The higher symmetry of the magnetic layer in perpendicular media increases the grain size dispersion. It is argued that out-of plane dispersion of the vertical axes of grains, important in longitudinal media, further enhances the differences between grain size distributions in these two types of media. The results are confirmed by experimental measurements.