Fiber optics for spin waves

Magnetic skyrmions in chiral magnets with the Dzyaloshinskii-Moriya interaction have received intensive attention because of their potential in prospective applications. Here, we theoretically demonstrate that another novel spin texture in chiral magnets-the chiral strip-domain wall (SDW)-can generate a deep one-dimensional potential well of magnetic origin. We show by micromagnetic simulations that the potential well caused by a SDW can serve as an internal channel to guide spin-wave (SW) propagation, which makes the ultrathin chiral magnet including the SDW become a reconfigurable self-cladding optic-fiber-like magnonic waveguide with a graded refractive index. Furthermore, we design logical NOT and NAND gates based on the state-modulated transmission property of the magnonic waveguide. We also reveal that a SDW can be reliably written into the gate arms using the Slonczewski spin torque. Finally, prospective applications of the observed potential well in other fields are envisioned. This work is expected to open new possibilities for SW guiding and manipulation in ultrathin magnetic nanostructures as well as to help shape the field of beam magnonics.