Decoupling nucleation and domain-wall propagation regimes in (Co/Pd)n multilayer nanostructures

In (Co/Pd)(n) multilayer dots with submicrometer diameters, it is understood that reversal is initiated by the nucleation of a small reversed region, followed by uninhibited expansion of the nucleus. The fact that the reversed domain expands with relative ease has been attributed to the fact that the field required to free a domain wall is much smaller than the field required to create the nucleus. In this work, we measured the angular dependence of the coercivity in individual 500-nm and 1-mu m (Co/Pd)(n) multilayer dots and show that the shape of this curve deviates from the Stoner-Wohlfarth-like form observed by others. We attribute this deviation to (1) the domain-wall depinning field exceeding the nucleation field when the reversal field has a large in-plane component and (2) exchange-spring-like behavior at the dots' edges due to ion-mill damage.