Magnetic vortex core observation in circular dots of permalloy

Spin structures of nanoscale magnetic dots are the subject of increasing sc ientific effort, as the confinement of spins imposed by the geometrical res trictions makes these structures comparable to some internal characteristic Length scales of the magnet. For a vortex (a ferromagnetic dot with a curl ing magnetic structure), a spot of perpendicular magnetization has been the oretically predicted to exist at the center of the vortex. Experimental evi dence for this magnetization spot is provided by magnetic force microscopy imaging of circular dots of permalloy (Ni80Fe20) 0.3 to 1 micrometer in dia meter and 50 nanometers thick.