Magnetic domain structure and magnetization reversal in (Co/Ni) and (Co/Pd) multilayers

The temporal behavior of magnetization reversal mechanism and domain structures of (Co/Ni) and (Co/Pd) multilayers have been studied using magneto-optical Kerr effect microscopy and magnetometry measurements. The domain size and nucleation field of (Co/Ni) multilayers were found to be reduced as the number of bilayers increases. On the other hand, (Co/Pd)_×10 multilayer has a much larger domain size, faster magnetization switching, and a higher nucleation field than that in (Co/Ni). From the imaging of magnetic domains, two different types were observed, namely, dendritic domains for (Co/Ni) and blocks type for (Co/Pd). From time dependence of magnetization reversal at a fixed applied magnetic field, it was revealed that the reversal mechanism in (Co/Ni) multilayer occurs by nucleation followed by domain propagation. Whereas, for (Co/Pd) multilayers, few large domains were observed, and they were found to expand at a faster rate until a complete saturation.