Nonreciprocal amplification of spin-wave signals

The research on spin wave is attracting more attentions and novel spin-wave based devices including nanometer size phase-shifter, logical gates, and spin-wave bus have been developed. In order to fully realize functions promised by spin waves, especially in cascaded signal processing, a device that can directly amplify spin-wave signal is indispensable. Ferromagnetic parametric amplifiers - amplifying spin-wave signals by pump waves whose frequencies are typically double of signal frequency, were proposed. So far, all demonstrated spin-wave amplification experiments reported by other groups have used ferrite insulating materials [1]. In this abstract, we report spin-wave amplification with a conducting metallic thin film as well as a new magnetic device property - nonreciprocal amplification of spin-wave signals even though the spin-wave propagation is reciprocal.