Yttrium iron garnet, a synthetic material, has magnetic properties that make it valuable in a wide range of applications including superconductors, data storage, magneto-optics and tunable microwave devices. Existing methods for exciting spin waves — the collective magnetic excitations within the material — are often complicated to incorporate into nanoscale electronic circuits. Wang et al., however, demonstrate a new method without the disadvantages of other methods, which phase shifts and disperses spin-waves within yttrium iron garnet solely using external electric fields without charge current.
The authors built a spin-wave waveguide and observed the resulting spin wave profiles in a stripe of yttrium iron garnet while applying an external microwave electric field. They modeled the spin-waves in the phase shifter to determine that the spin-wave behavior occurs due to the microwave electric field generating time-dependent, non-collinear magnetization rotations at the sample edges through magneto-electric coupling.
They found that the excited edge rotation and spin wave amplitude increase as the electric field increases, and their spatial profiles vary with the electric field direction. The authors also found similar spin wave behavior in other magneto-electric materials they investigated.
Based on their conclusions, the magneto-electric coupling means that variation in the electric field can be used to control the excitation and dispersion of spin-waves in yttrium iron garnet, making the material tunable with the phase shifter. Furthermore, while the intensity and direction of the electric field affects spin-wave phase shift, this shift is independent of the electric field’s frequency in the microwave range explored.
Source: “Electric field controlled spin waveguide phase shifter in YIG,” by Xi-guang Wang, L. Chotorlishvili, Guang-hua Guo, and J. Berakdar, Journal of Applied Physics (2018). The article can be accessed at https://doi.org/10.1063/1.5037958.