Figure 5
Illustration: Alan Stonebraker

Figure 5: How polarization emerges in a spin wave (magnon). (a) The classical picture of a spin wave in a ferromagnet: the spin (red arrow) precesses about a fixed axis (blue). The deviation is measured by the black arrows. (b) According to Eq. (1), as a spin-wave packet propagates along Q, it will also carry an electric dipole moment.