Acoustic Spin Waves

Spin waves in ferromagnets are coherent dispersive waves, with typical frequencies in the low GHz regime and wavelengths from hundreds of nanometers to a few micrometers. Recent interest for spin waves is motivated by the possibility of their integration in nano-scale devices for high-speed and low-power signal processing. However, generation of spin waves with high amplitudes---and their detection---is challenging due to the mismatch of wavelengths with electromagnetic waves in free space, which is of the order of several centimeters. Using hybrid piezoelectric/magnetic systems we have generated large amplitude spin waves mediated by magneto-elasticity with up to 25 degrees variation in the magnetization orientation. We present direct imaging and quantification of both standing and propagating spin waves with different wavelengths, over large distances up to several millimeters, orders of magnitude longer than previously achieved.