A magnetic multilayer of the structure substrate/Pt-15 nm/Co-0.8 nm/Pt-wedge(0-7 nm)/Co-0.6 nm/Pt-2 nm is characterized by perpendicular anisotropy of both Co layers. For a Pt spacer thickness tPt≤2.6nm, the magnetization reversal of the Co-layers occurs cooperatively, while for larger tPt, it occurs sequentially. The Co-layer with 0.6 nm thickness (Co^S) is magnetically softer than the second one (Co^H). In the 2.6≤tPt≤3.0 nm range, there are significant changes of the switching field due to a strong gradient of the interlayer coupling. In this region, the magnetization reversal in the Co^S layer takes place reversibly by the propagation of a single, straight domain wall. This specific nature of magnetization reversal is explained by a decelerated motion of the domain wall observed both for the direction corresponding to the increasing, as well as decreasing coupling energy.