  Optimizing magnetic thin films for nanotechnologies often requires imaging
nanoscale magnetic domain patterns via magnetic microscopy. The finite size of
the image may however significantly affect the characterization of the observed
magnetic states. We evaluated finite image size effects on the characterization
of a variety of stripe and bubble domain patterns exhibited by ferromagnetic
Co/Pt multilayers with perpendicular magnetic anisotropy, where the domain size
(stripe width and bubble diameter) is around 100 nm. If the image size is too
small, below ~ 5 microns, it may cause a significant underestimation of average
domain size and overestimation of domain density by up to a factor 5 when
reducing the image size from about 20 microns to about a 1 microns. Using a
criterion based on how the excess density evolves with image size, we found
that to obtain reliable statistical estimates of domain density and average
domain size, the image needs to be large enough, and include at least about 100
stripes or about 2500 bubbles.
