Skyrmion State in Elemental Co Induced by Strong Dzyaloshinskii-Moriya Interaction

Skyrmions are stable spin textures with chiral rotations from one spin-up moment to another across the center. Most of the materials bearing the Skyrmion state are magnetic ultrathin films deposited on heavy metals. Based on theoretical calculations, we show that the Skyrmion state exists also in the metastable phase of Co. Strong Dyzaloshiskii-Moriya (DM) interactions with meanwhile large isotropic exchange have been found in this material. Detailed analysis reveals that the DM interaction is caused by directional anisotropic hopping between atomic orbitals, following the perturbation theory. Although the DM interactions between different atomic pairs partly cancels with each other, the net interaction is sufficient to induce a chiral left-handed screw spiral. The spiral state has a wavelength about 180 nanometers along either [100] or [110] crystalline directions. The critical external magnetic field needed to stabilize the Skyrmion state is estimated to be 2.9 T at zero temperature, which is significantly lower than that required to stabilize the Skyrmion state in magnetic ultrathin films on heavy metals.