Single chiral skyrmions in ultrathin magnetic films

Abstract

The stability and sizes of chiral skyrmions in ultrathin magnetic films are calculated accounting for the isotropic exchange, Dzyaloshinskii-Moriya exchange interaction (DMI), and out-of-plane magnetic anisotropy within micromagnetic approach. Bloch skyrmions in ultrathin magnetic films with B20 cubic crystal structure (MnSi, FeGe) and Neel skyrmions in ultrathin films and multilayers Co/X (X = Ir, Pd, Pt) are considered. The generalized DeBonte ansatz is used to describe the inhomogeneous skyrmion magnetization. The single skyrmion metastability/instability area, skyrmion radius, and skyrmion width are found analytically as a function of DMI strength d. It is shown that the single chiral skyrmions are metastable in infinite magnetic films below a critical value of DMI dc, and do not exist at d > dc. The calculated skyrmion radius increases as d increases and diverges at d → dc - 0, whereas the skyrmion width increases monotonically as d increases up to dc without any singularities. The calculated skyrmion width is essentially smaller than the one calculated within the generalized domain wall model.