Magnetic domain evolution in permalloy mesoscopic dots

Permalloy (Ni/sub 80/Fe/sub 20/) squares (30 nm thick and w /spl mu/m wide; 1/spl les/w/spl les/200 /spl mu/m) and circular disks (30 nm thick and r /spl mu/m diameter; 1/spl les/r/spl les/200 /spl mu/m) prepared on a GaAs(100) substrate were observed in both their demagnetized and remanent states by magnetic force microscopy (MFM) associated with non-contact atomic force microscopy (NC-AFM). The squares (2/spl les/w /spl mu/m) exhibited conventional closure domains and the corner plays a very important role in creating new walls. The circular disks, on the other hand, formed either vortex domain (5/spl les/r/spl les/20 /spl mu/m) or multi-domain (50/spl les/r /spl mu/m) states. The magnetization rotation is observed by MFM to change according to the size and shape of the elements. The MFM observations are supported by micromagnetic calculations which confirm the effect of the corner on the domain wall formation.