Microstructural origin of switching field distribution in patterned CoPd multilayer nanodots

We have identified an important microstructural origin of the switching field distribution (SFD) in patterned CoPd multilayer nanodots. In this study, we patterned a marked array of 115 nm CoPd nanodots on 50-nm -thick Si3 N4 substrate. We identified the dots with unusually small and large (>2 standard deviations of the mean) switching fields with magnetic force microscopy, followed by microstructural characterization of the same dots with transmission electron microscopy (TEM). From electron diffraction, we found that most nanodots with small switching fields have strong (200) spots, whereas those with large switching fields lack these spots. While bright-field TEM images reveal an average grain size of 7 nm, dark-field images of the (200) spots reveal on average, a single grain of >10 nm in lateral dimensions. Since we observed a direct correlation between strong (200) reflections and small reversal fields, we conclude that the largest grain in each nanodot, with an in-plane [001] is the likely cause for premature switching, which in turn defines the SFD of this array.