Magnetic vortices induced by a moving tip
  A two-dimensional easy-plane ferromagnetic substrate, interacting with a dipolar tip which is magnetised perpendicular with respect to the easy plane is studied numerically by solving the Landau-Lifshitz Gilbert equation. Due to the symmetry of the dipolar field of the tip, in addition to the collinear structure a magnetic vortex structure becomes stable. It is robust against excitations caused by the motion of the tip. We show that for high excitations the system may perform a transition between the two states. The influence of domain walls, which may also induce this transition, is examined. 
Martin P. Magiera and Alfred Hucht and Haye Hinrichsen and Silvio R.   Dahmen and Dietrich E. Wolf
cond-mat.other cond-mat.stat-mech