Stable two- and three-dimensional geometrically constrained magnetic structures: The action of magnetic fields

We show that equilibrium geometrically constrained domain patterns are two- or three-dimensional magnetic configurations localized around sharp constrictions. Their typical size w depends on both the length d and cross size a of the constriction. When d<L-0 the value wsimilar or equal tomin[(2a+d),L-0], where L-0 is the conventional wall width. The localized structures undergo small deformation under magnetic fields and at a threshold field they detach from the constriction and magnetization reversal occurs.