F. Tejo, A. Riveros, J. Escrig, K. Y. Guslienko and O. Chubykalo-Fesenko
We investigate the dependence of the Néel skyrmion size and stability on perpendicular magnetic field in ultrathin circular magnetic dots with out-of-plane anisotropy and interfacial Dzyaloshinskii-Moriya exchange interaction. Our results show the existence of two distinct dependencies of the skyrmion radius on the applied field and dot size. In the case of skyrmions stable at zero field, their radius strongly
increases with the field applied parallel to the skyrmion core until skyrmion reaches the metastability region and this dependence slows down. More common metastable skyrmions demonstrate a weaker
increase of their size as a function of the field until some critical field value at which these skyrmions drastically increase in size showing a hysteretic behavior with coexistence of small and large radius
skyrmions and small energy barriers between them. The first case is also characterized by a strong dependence of the skyrmion radius on the dot diameter, while in the second case this dependence is
very weak.
Fig.1. Ultrathin circular ferromagnetic (FM) nanodot on a heavy metal (HM) substrate. The Néel skyrmion magnetization profile is shown by the color map. The applied magnetic field is in the z-direction and is perpendicular to the dot plane.
