Nonreciprocity of spin waves in the conical helix state
N. Ogawa, Laura Köhler, Markus Garst, S. Toyoda, S. Seki, Yoshinori Tokura
Abstract
Significance While spin waves in conventional ferromagnets are well understood, those in more complicated magnets hosting spatially textured magnetization, such as helical/conical and skyrmion/hedgehog configurations, are less explored. We investigate experimentally and theoretically the spin waves of the conical spin helix in a chiral magnet with the help of Brillouin light scattering. We discovered that the dynamics of the conical spin helix is characterized by a distinct nonreciprocity with spin waves preferentially propagating in a specific direction controlled by the orientation of the magnetic field. Our work therefore demonstrates that all the spin phases of bulk chiral magnets allow, in principle, the realization of a switchable spin wave diode functionality.