Emergent topological spin structures in the centrosymmetric cubic perovskite SrFeO3

The skyrmion crystal (SkX) characterized by a triple-q helical spin modulation has been reported to be a unique topological state that competes with the single-q helimagnetic order in noncentrosymmetric materials with Dzyaloshinskii-Moriya (DM) interactions. Here, we report the discovery of a rich variety of multiple-q helimagnetic spin structures in the centrosymmetric cubic perovskite SrFeO3 without DM interactions. On the basis of neutron diffraction measurements, we have identified two types of robust multiple-q spin structures that appear in the absence of external magnetic fields: an anisotropic double-q spin spiral and an isotropic quadruple-q spiral hosting a three-dimensional lattice of topological singularities. The present system not only diversifies the family of SkX host materials but furthermore provides an experimental missing link between centrosymmetric lattices and topological helimagnetic order. It also offers perspectives for integration of SkXs into oxide electronic devices.