Coupling of terahertz light with nanometre-wavelength magnon modes via spin–orbit torque

Abstract Spin-based technologies can operate at terahertz frequencies but require manipulation techniques that work ultrafast timescales to become practical. For instance, devices based on spin waves, also known as magnons, efficient generation of high-energy exchange waves nanometre wavelengths. To achieve this, a substantial coupling is needed between the magnon modes and an electro-magnetic stimulus such coherent field pulse. However, it has been difficult excite non-uniform efficiently using light because large momentum mismatch submillimetre-wave radiation nanometre-sized waves. Here we improve light–matter interaction by engineering thin films exploit relativistic spin–orbit torques are confined interfaces heavy metal/ferromagnet heterostructures. We able spin-wave with up 0.6 THz wavelengths short 6 nm broadband radiation. Numerical simulations demonstrate exchange-dominated magnons originates solely from interfacial torques. Our results general applicability other magnetic multilayered structures, offer prospect nanoscale control high-frequency signals.