Magnetization switching behavior in single dots of an epitaxially grown Co/Pt multilayer with various dot diameters ranging from 120 to 1600 nm haven been studied. All the dots used in this study are considered to be of the nucleation type switching behavior from the angular dependence of the switching field. However, detailed analysis of the thermally activated magnetization switching reveals that there is a critical diameter of 400 nm above which the switching process changes. For the dot diameter smaller than 400 nm, the switching behavior is well explained by the nucleation process based on the single-energy barrier model. On the other hand, the switching behavior for the dots larger than 400 nm obviously deviates from that for the dots smaller than 400 nm and can be plausibly explained by the multi-barrier model.
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