The Development of a Novel Figure of Merit to Analyze Strain-Mediated Magnetoelectric Antennas

Strain-mediated magnetoelastic composite materials are being considered for communication in lossy environments. Their consideration is attributable to predictions stating order of magnitude improvements over current antenna technology. The magnetic antenna design considered herein consists of three layers: 1) a piezoelectric layer, 2) a linear elastic layer, and 3) a magnetoelastic layer. The antenna operates by mediating strain through the device in a resonant bending mode. The magnetoelastic layer is stressed which results in a changing magnetization ultimately leading to a changing magnetostatic field in free space which acts as a signal for information transfer. In order to prove the efficacy of this approach finite element models have been developed to aid in the design and optimization process. Where these models fall short is in their overall run-time to fully resolve the coupled dynamics. It is for this reason that the work presented in this thesis focuses on the development of a figure of merit capable of predicting optimal bias conditions and geometries needing only the data from a static bias study from FEA. The material level magnetomechanical coupling factor is chosen as the foundation for the figure of merit. The figure of merit is then augmented to include structure level information regarding the demagnetizing field and the non-uniform stress distribution. The main results presented are the effects of including demagnetization and stress distributions, and most importantly the ability of the metric to predict the change in magnetization of the device. It is shown that for aspect ratios greater than roughly 2.5 the metric trends the same as the change in magnetization predicted by finite element simulations. The region of disagreement between the metric and the fully resolved finite element simulation is explained by tying back to underlying assumptions made during the formulation of the magnetometric demagnetization factor used in the analysis. The case is made for the figure of merit to be included in the analysis of strain-mediated antennas for its ability to find optimum designs while reducing the overall simulation run-time by an order of magnitude.