Magneto-optical Kerr effect measurements performed on ͑0.3 nm Co/x Pt) 15 multilayers with xϭ0.3-2.0 nm showed all samples to exhibit strong perpendicular magnetic anisotropy. Recent work has shown that for compositions near ͑0.3 nm Co/1.2 nm Pt͒ 15 , both polar Kerr rotation and ellipticity exhibit bimodal reversals in which the major hysteresis loops have two distinct field-dependent steps due to the contributions of two magnetic phases. To better understand this bimodal magnetization phenomenon, Kerr rotation and ellipticity were determined as a function of radial position from the center to the edge of this disk sample. These measurements exhibit a continuous variation from two-step ͑bimodal͒ behavior in the center to single-step ͑unimodal͒ behavior at the edge. Since these films were deposited via MBE with a heated substrate, it is believed that this phenomenon is related to thermally induced variations in interface effects such as alloying, abruptness, and morphology.