Reversal mechanism of submicron patterned CoNi/Pt multilayers

With laser interference lithography Co50Ni50/Pt multilayers with perpendicular magnetic anisotropy have been patterned into regular matrices of submicron sized dots. Their magnetic properties have been studied with Vibrating Sample Magnetometry, Compared to continuous multilayers (H-c, = 15 kA/m) the coercivity for the patterned multilayers is much larger (H-c, = 115-270 kA/m), Though the hysteresis curves of 180 nm dots and 60 nm dots have identical shapes, virgin curves seem to indicate that the 180 nm dots are multidomain while the 60 nm dots are single domain. The latter has been confirmed with Magnetic Force Microscopy observations.