UCLA

Magnetic materials have distinct behaviors attributed to their underlying spin dynamics. At radio frequencies, these behaviors have long made magnetic insulators called ferrites essential in the design of nonreciprocal devices such as circulators or isolators. However, the capabilities offered by spin dynamics are far from being fully realized. This dissertation focuses on two features of spin dynamics in the context of their application to designing new radio frequency devices. The first part of the dissertation examines nonlinearities inherent in spin dynamics to propose a new type of magnetic field sensor called the radio frequency precession modulation (RPM) sensor. Existing sensor types are unable to achieve high sensitivities without being impractical in terms of size or power consumption which limits their potential usefulness. In contrast, RPM sensors simultaneously have high sensitivity, small size, and low power consumption. The theory of RPM sensors is developed and verified through simulation. A prototype is constructed, and experimental characterizations are consistent with theoretical predictions. The prototype exhibits a sensitivity of 11.6 pT/Hz1/2 with a volume of 0.056 mm3 and a power consumption of -41 dBm which is already competitive with existing sensors. The second part of the dissertation examines the magnetoelastic coupling of spin dynamics to mechanical stress to analyze a new type of antenna called the mechanically driven magnetoelectric antenna. These antennas employ magnetoelectric multiferroic composites to achieve smaller sizes and higher efficiencies as compared to existing antennas. Given that the research on these antennas is still in its early stages, the approaches to modeling them have been largely deficient, particularly with regards to the magnetoelastic coupling component of their operation. For accurate modeling that provides guidance in design and operation, the physics of magnetoelastic coupling is considered. Material-dependent conditions that maximize the coupling are found, and symbolic expressions explicitly relating the coupling to operational parameters and material properties are derived. Comprehensive numerical evaluations of the expressions reveal characteristics of the coupling as well as the influence of the operational parameters and material properties. The results provide insight and serve as a foundation upon which more comprehensive models can be constructed.