We describe small-angle neutron scattering measurements of the magnetic cluster size distributions
for several longitudinal magnetic recording media. We find that the average magnetic cluster size is
slightly larger than the average physical grain size, that there is a broad distribution of cluster sizes,
and that the cluster size is inversely correlated to the media signal-to-noise ratio. These results show
that intergranular magnetic coupling in these media is small and they provide empirical data for the
cluster-size distribution that can be incorporated into models of magnetic recording.