Transmission of electrical signals by spin-wave interconversion in a magnetic insulator

The energy bandgap of an insulator is large enough to prevent electron excitation and electrical conduction. But in addition to charge, an electron also has spin, and the collective motion of spin can propagateand so transfer a signalin some insulators. This motion is called a spin wave and is usually excited using magnetic fields. Here we show that a spin wave in an insulator can be generated and detected using spin-Hall effects, which enable the direct conversion of an electric signal into a spin wave, and its subsequent transmission through (and recovery from) an insulator over macroscopic distances. First, we show evidence for the transfer of spin angular momentum between an insulator magnet Y 3 Fe 5 O 12 and a platinum film. This transfer allows direct conversion of an electric current in the platinum film to a spin wave in the Y ₃ Fe ₅ O ₁₂ via spin-Hall effects^4-11. Second, making use of the transfer in a Pt/Y ₃ Fe ₅ O ₁₂ /Pt system, we demonstrate that an electric current in one metal film induces voltage in the other, far distant, metal film. Specifically, the applied electric current is converted into spin angular momentum owing to the spin-Hall effect in the first platinum film; the angular momentum is then carried by a spin wave in the insulating Y ₃ Fe ₅ O ₁₂ layer; at the distant platinum film, the spin angular momentum of the spin wave is converted back to an electric voltage. This effect can be switched on and off using a magnetic field. Weak spin damping in Y ₃ Fe ₅ O ₁₂ is responsible for its transparency for the transmission of spin angular momentum. This hybrid electrical transmission method potentially offers a means of innovative signal delivery in electrical circuits and devices.