Origins of switching field distributions in perpendicular magnetic nanodot arrays

We studied the reversal properties of perpendicularly magnetized Co∕Pd nanodots from 100to50nm in diameter fabricated using electron beam lithography. Polycrystalline Co∕Pd multilayers show considerable differences in the switching field distribution (SFD) depending on the seed layer used. With a Ta seed layer, we reduced the SFD to approximately 5% of the average switching field. To rule out effects of grain boundaries, we also fabricated nanodot arrays from epitaxial Co∕Pd superlattices. Although significant improvement in SFDs are obtained using epitaxial superlattices, our results indicate that grain boundary variation within nanodots is not the primary origin of SFD broadening that occurs with nanopatterning.