Straight motion of half-skyrmion topological defects in thin magnetic films with stripe domains

In thin magnetic films with perpendicular magnetic anisotropy, an up-down stripe-domain structure can be originated, on a mesoscopic scale comparable with film thickness, by the competition between short-range exchange coupling and long-range magnetic dipole-dipole interaction. Even in the absence of quenched disorder, topological defects can develop in the stripe pattern due to large amplitude fluctuations occurring in two dimensions. Here we investigate the dynamic behavior of magnetic edge dislocations (with skyrmion number Qs=±1/2) in a N2+-implanted Fe film, with thickness t=78 nm and stripe domain period P=100 nm. Combining evidence from magnetic force microscopy data, micromagnetic simulations and a theory based on the Thiele equation, the defects were found to undergo a straight displacement. When a moderate magnetic field is applied in plane along the stripes axis, the displacement may be either in the direction of the applied field or in the opposite direction, depending on the in-plane magnetization in the topological magnetic defects, but irrespective of the out-of-plane magnetization in the stripe domains. A relationship is established between the vanishing skyrmion number, Qs=0, of the topological defects embedded in the stripe pattern and the straight character of the motion, suggesting that FeN films might be used for future spintronic devices intrinsically free from the undesired skyrmion Hall effect. Finally, it is remarkable that, in such systems with a "rotatable anisotropy", the stripes axis and consequently the motion of defects can be arbitrarily chosen to take place along any in-plane direction.