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The dot size dependence of the magnetization reversal process in perpendicularly magnetized L10-FePt dot arrays has been investigated in terms of minor loop measurement and magnetic domain observation. For the dots with diameters of 0.25 and 1 mum, the initial applied field (Hin sat) required to saturate the coercivity in the minor loop starting from the thermally demagnetized state is smaller than saturated coercivity (Hc sat), indicating a typical nucleation-type magnetization reversal process. For the dots with diameters of 2.3 and 5 mum, on the other hand, Hin sat is larger than Hc sat. The magnetic force microscopy images show that the field to wipe out domain walls increases with the dot size, which is consistent with minor loop measurements. The phenomenological analysis for the dots with diameters of 0.25 and 1 mum indicates that irrespective of the dot size the annealing reduces the size of the defect regions and leads to the enhancement of the coercivity due to the recovery from the microfabrication damage.