Magnetization processes in submicronic Co dots studied by means of micromagnetic calculations

The magnetization nucleation mechanisms taking place in "perfect" submicronic cobalt dots obtained by means of three-dimensional micromagnetic simulations are shown. Attention is focused on the study of the transition from parallel-to-plane to perpendicular-to-plane magnetization occurring as the thickness of the dot is increased. Simulations show different nucleation and magnetization reversal mechanisms as thickness varies, For a 35 nm dot, nucleation of stripe domains takes place. Stripe domains evolve with the decrease of the in-plane applied field towards a configuration of "bended stripe" domains as a result of the need for a lateral flux closure. The same nucleation mechanism has been found for thicker dots and is responsible for the appearance of diagonal domains for high thicknesses. For 25 nm thick dots no stripe domains are present and a full in-plane magnetization configuration has been obtained for which flux closure takes place with the formation of two distorted vortices at both sides of the dot. Copyright (C) 1998 Elsevier Science B.V.