Non-Reciprocity and Non-linearity in Engineered Magneto-Acoustic Devices

Nonreciprocity, the property of merit for a variety of RF components such as isolators and circulators, is typically difficult to achieve with the magnitude required for applications. Many systems which demonstrate non-reciprocity are not suitable for scaling to the size, weight, and power required for applications, or do not exhibit a sufficient intensity of the effect for applications relevance. One such physical system which generally does not exhibit non-reciprocity is that of acoustic waves. I will discuss discoveries of non-reciprocity and non-linearity in surface acoustic waves interacting with magnetic materials. Giant Nonreciprocity of 48.4 dB (ratio of 1:100,000) is achieved in the transmission of surface acoustic waves on a lithium niobate substrate coated with ferromagnet/insulator/ferromagnet (FeGaB/Al2O3/FeGaB) multilayer structure. This same structure has now also demonstrated very large phase shifts due to a similar interaction, and the nature of the magnetic ordering and coupling to the acoustic system will be discussed. Nonlinearity will also be discussed and is demonstrated using focused interdigitated transistors employing curved fingers, in contrast to the straight fingers typically used. These transducers are engineered to concentrate acoustic energy towards a small region in the center of the device allowing driven magnetic precession much higher than was previously possible. Enhanced acoustic absorption and modeling of the response will be shown. These devices promise functionality which outperforms current state of the art high frequency devices in a novel acoustic wave system that facilitates unprecedented size, weight, and power reduction.