Scattering and Goos–Hänchen shift of antiferromagnetic spin waves under the spatial change of exchange interaction

Abstract

We theoretically studied the scattering properties of antiferromagnetic spin waves at the interface across which the exchange coefficient varies, with a particular focus on manifestations of spin-wave polarization. Based on the equations of motion for the dynamics of antiferromagnets, the scattering problems for spin waves are solved analytically in the presence of magnetic anisotropy and an external magnetic field in two dimensions. In particular, we show that right- and left-handed spin waves exhibit distinct scattering behaviors in the presence of an external field that breaks the degeneracy between the two modes. Furthermore, by calculating the Goos–Hänchen shift from the two-dimensional scattering solutions, we show that right- and left-handed spin waves with identical incident spatial wave functions can be spatially separated after being reflected from the interface. These two results indicate that the interface harboring the spatial change in the exchange coefficient can serve as an antiferromagnetic spin-wave polarizer as well as a polarizing beam splitter, which can be utilized to control the polarization degree of freedom of magnonic devices.