The Microwave Magnetoelectirc Mechanism In Laminated Magnetoelectric Structure And Application In Microwave Devices

Magnetoelectric(ME) tunable microwave device is consisted of traditionalmicrostrip structure and novel ME composite materials. Because of its largemagnetic field tunability and small range of electric precisely tuning characteristics,ME microwave devices have highly application value in microwave multifunctionaldevices. In order to study the microwave ME mechanism in the laminated MEstructure, firstly, This paper proposed a theoretical model for ferromagneticresonance(FMR) tuning by the in-plane and out-of-plane bias magnetic field basedon the theory of Smith-Beljers and free energy density of the ferrite. According to thetheoretical model prediction results, the influence of the in-plane magnetic field inFMR shift comes from the uniaxial anisotropy field and fourth order magneticanisotropy field. The influence of the out-of-plane magnetic field in FMR shiftcomes from the cosine term of the saturation magnetization. Subsequently, atheoretical model based on ferrite-piezoelectric layered ME multiferro-materialsabout three phases FMR frequency shift is discussed. This model is accomplishedthrough the geometry and MEconstant of ferrite-piezoelectric layers. The resultsshow that, when the in-plane dimensions of the laminated structure is30times largerthan the thickness of the ferromagnetic layer, the FMR shift caused by the dimensionof the ferromagnetic layer can not be ignored.Secondly, theoretical models of the electric field tuning FMR frequency shiftare proposed based on the dual-layers and tri-layers of the ME laminated structure,and it’s decided by the bonding mode between the ME layers. For dual ME layers,this model can effectively predict the experimental phenomenon that the FMRfrequency increases under parallel magnetic field while decreases under verticalmagnetic field when the electric field changes. We also find that the electric fieldfails to tune the FMR frequency when the angle is33.5°. For Tri ME layers, thismodel can also effectively predict the phenomenon that the stress of the laminatedstructure has a obviously increasing trend when the piezoelectric coefficient isincreased. Moreover, the FMR frequency shift will be more obvious according to the greater saturation magnetization and ME coefficient.Finally, a numerical analysis model of the ME devices based on theelectromagnetic simulation software Ansoft HFSS is established, and the accuracyand reliability of this numerical analysis model is confirmed by combining with thesimulation results, experimental results and theoretical results. On this basis of thissimulation model, in order to improve the properties of the microwave filters, asimulation model of microwave ME dual-band stop filter including two ME layers isfabricated and characterized using the tunability of piezoelectric effect and FMR.The results showed that, the theoretical results and the simulation results are in goodagreement. However, there still exist some issues that the absorption peak of FMR issharp and the bandwidth is quite narrow. In order to improve these issues, a MEmicrowave band-stop filter based on the step microstrip structure is designed andanalysed. The results show that the step microstrip structure can effectively enhancethe coupling effect of the magnetic tenability, the FMR energy absorption and expandthe attenuation and bandwidth of the stop-band.