Magnetization configuration and magnetic switching behavior in two types, P-I and P-II, of submicrometer Pac-man-shaped Ni80Fe20 magnetic elements are studied using both magnetic force microscopy (MFM) and numerical simulation. It was found that a slight variation in the shape of the elements has a striking influence on the internal magnetic structures and switching field distribution. In particular, the vortex-formation-driven switching is replaced by quasi-coherent reversal by removing the central core part at the center of element. The sensitive dependence of remanent magnetic configuration and switching behavior on sample geometry is discussed in terms of the competition between the exchange and demagnetizing energy terms. © 2005 IEEE.