Theory of 360° domain walls in thin ferromagnetic films

An analytical and computational study of 360° domain walls in thin uniaxial ferromagnetic films is presented. The existence of stable one-dimensional 360° domain wall solutions both with and without the applied field is demonstrated in a reduced thin film micromagnetic model. The wall energy is found to depend rather strongly on the orientation of the wall and the wall width significantly grows when the strength of the magnetostatic forces increases. It is also shown that a critical reverse field is required to break up a 360° domain wall into a pair of 180° walls. The stability of the 360° walls in two-dimensional films of finite extent is demonstrated numerically and the stability with respect to slow modulations in extended films is demonstrated analytically. These domain wall solutions are shown to play an important role in magnetization reversal. In particular, it is found that the presence of 360° domain walls may result in nonuniqueness of the observed magnetization patterns during repeated cycles of magnetization reversal by pulsed fields.