Nonreciprocal Magnetostatic Surface Wave in Thin Ferromagnetic Film
Abstract
Interest in the nonreciprocal property of waves inside the magnetic material starts with its current advancement in the field of passive devices. In current technology passive devices without magnetic cores are realized on a silicon chip, usually these devices are lossy and bigger in size. Passive devices constructed with magnetic core material such as isolators, circulators, phase shifters, and gyrators; gives us the chance to minimize such losses. Nonreciprocity in magnetic material is due to the anisotropic property of permeability, it is complex in nature and represent in 3×3 matrix form. We can control the wave flow inside the nonreciprocal devices by making some changes in the matrix. This thesis work includes modeling, simulation, and investigation of ferromagnetic material to enhance nonreciprocity effect. We perform physical measurement on actual devices and then use the same parameters to design the model in comsol multiphysics software to verify the nonreciprocity. This thesis work also suggests different ways to suppress eddy current losses to increase the nonreciprocity effect. Comsol is a simulation tool for our RF passive device model containing magnetic core material. All simulation results were obtaining from comsol; it is used as to model the device and set different parameter defined for ferromagnetic devices. We successfully investigate the nonreciprocity inside the magnetic material by analyzing scattering parameters (S12 and S21). The design of any nonreciprocal device is a big challenge because propagation losses are more, even a small change in structure suppress the nonreciprocity effect. This work has shown that by using these improved configurations we can reduce loss and enhance the overall device performance. Nonreciprocal spin iv wave has been observed in the ferromagnetic thin film by placing it between neighboring metallic layer. By proper selection of line width, spacing between signal lines, position, and thickness of films, the maximum nonreciprocity up to -26.0 dB for NR-Amplitude and -180.0° phase difference for NR-Phase is reported.
