Magnetization reversal in Co∕Pd nanostructures and films

The magnetic field required to reverse a Co∕Pd multilayer film with perpendicular anisotropy is greatly increased when the film is deposited onto patterned islands. The variation of the reversal field with Co thickness demonstrates that the island switching field is determined principally by the anisotropy. For sufficiently small islands the reversal field is close to that calculated using the Stoner–Wohlfarth (SW) model and these small islands show the expected SW angle dependence. A similar SW angle dependence is also observed for the larger islands. We propose that for the larger islands reversal is governed by a nucleation event, which has SW characteristics, followed by rapid domain wall motion.