Excitation Spectrum of the Topological Spin Order in SrFeO3

Spin dynamics in multi-q noncoplanar ordered structures (e.g. skyrmion lattices) is an active topic of research. The cubic perovskite SrFeO3 has a variety of multiple-q magnetic phases including a recently identified 3D topological spin order that is analogous to a skyrmion lattice. This highly symmetric noncoplanar phase on a cubic lattice is characterized by a star of 4 equivalent magnetic propagation vectors pointing along the {111} cubic directions. In contrast to the less symmetric ground-state phase, which forms multiple magnetic domains, the quadruple-q phase does not suffer from magnetic twinning and should result in cleaner inelastic spectra. Here we propose to map out spin-wave excitations in SrFeO3 across the magnetic phase transitions between zero-field phases I, II, and III. The results will help us understand and model the dynamics of topological spin structures.