Spin-wave propagation in cubic anisotropic materials

The information carrier of modern technologies is the electron charge, whose transport inevitably generates Joule heating. Spin waves, the collective precessional motion of electron spins, do not involve moving charges and thus avoid Joule heating. In this respect, magnonic devices in which the information is carried by spin waves attract interest for low-power computing. However, implementation of magnonic devices for practical use suffers from a low spin-wave signal and on/off ratio. Here, we demonstrate that cubic anisotropic materials can enhance spin-wave signals by improving spin-wave amplitude as well as group velocity and attenuation length. Furthermore, cubic anisotropic materials show an enhanced on/off ratio through a laterally localized edge mode, which closely mimics the gate-controlled conducting channel in traditional field-effect transistors. These attractive features of cubic anisotropic materials will invigorate magnonics research towards wave-based functional devices. Layers of magnetic materials can boost the signal in magnonic devices, opening a new way to realize low-power computing. A promising low-power alternative to conventional electronics, magnonics uses propagating disturbances in magnetic ordering known as spin waves, or magnons. But magnonic applications have been limited by low spin-wave signals and poor on/off ratios. Now, Kyung-Jin Lee from Korea University in Seoul and his colleagues have addressed both limitations by using thin layers of iron to guide spin waves. The cubic anisotropy of iron gives enhanced spin wave properties, which are expected to greatly improve the signal-to-noise ratios of magnonic devices. Furthermore, the cubic anisotropy enhances the on/off ratio. This demonstration will allow a three-terminal spin-wave logic function to be added to existing magnonic functionalities. We experimentally demonstrate that the spin-wave propagation in the hard-axis direction of an epitaxial Fe waveguide with a cubic anisotropy shows an enhanced spin-wave signal by improving spin-wave amplitude as well as group velocity and attenuation length. Schematic illustrations of a, easy-easy case (both directions of the magnetization and spin-wave propagation are in the easy axis) and b, hard-hard case (both directions of the magnetization and spin-wave propagation are in the hard axis). Magnetic-field dependences of spin-wave amplitude for c, easy-easy case and d, hard-hard case. e, Spin-wave attenuation length and f, group velocity as a function of the magnetic field.