Tunable acoustic wave rectification in anisotropic magnets

An acoustic wave, a flow of elastic energy, has been widely integrated into modern electronics to enable various functions, including sensing, communication, signal filtering, etc. In conventional media, acoustic waves follow a reciprocity rule, having an equal possibility for the forward and backward propagation and, thus, allowing for the interference between reflected and original waves in the real application. This interference not only suppresses the transmission efficiency but also risks breaking device structure due to the formation of standing waves. In the end, these features created by reciprocity limit the further development of acoustic waves based applications. A nonreciprocal acoustic waves device is highly desired. To break the symmetry of the propagation, here, we employ magneto-rotation coupling [AIP Conf. Proc. 29, 542 (1976)] to capture the chirality of the acoustic waves in a perpendicularly anisotropic ultra-thin film Ta/CoFeB(1.6 nm)/MgO, achieving a giant nonreciprocal acoustic wave attenuation with a rectification ratio up to 77$\%$.