Magnetoelectric (ME) Effect And Structural Optimization Of The Flexible Magnetoelectric Torque (MET) Device

Magnetoelectric (ME) effect is the coupling between themagnetization (M) and the electric polarization (P). Materials with MEeffect can be used in storage, sensors, energy harvester, energytransducer and etc. ME effect is a hot research topic in the world.Flexible magnetoelectric torque (MET) device is a new kind ofmagnetoelectric device with a strong magnetoelectric effect. It is akind of MET device. MET device is constructed from the magnet andpiezoelectric phase. The ME effect of the flexible MET device could beimproved by bonding the piezoelectric phase and elastic layers. Thealternating magnetic field and the permanent magnet installed on thesupporting layer could couple together to produce ME voltage output.The flexible MET device, which is different from traditional ME layereddevices that contain magnetostrictive materials, has the advantagesof simple structure, low price and high ME coefficient, low resonantfreuqnecy, and so on. It could effectively detect magnetic field signaland realize magnetoelectric energy conversion. Especially it has good compatibility with the modern electronic circuit. In this thesis, wefocused on the research of a novel flexible MET device.At first, we introduce the preparation methods of traditionalmagnetoelectric divices, the structures and the mechanism of themagnetoelectric effect, and analyze the development bottleneck forthe traditional magnetoelectric devices. The coupling field theory ofa flexible MET device with a composite structure of permanentmagnet/piezoelectric phase/elastic layer has been proposed. Weexplain the basic principle of this model, optimize the structural offlexible parts, study the magnetoelectric effect, and improve thepreparation technology, Based on these results, we successfullydesign and set up the related experiment equipment. We found thatthe testing deviation of production is reduced within five over onethousand.A series of relations between the magnetoelectric coefficient andthe geometry of the magnetoelectric device, remanence of thepermanent magnet, piezoelectric constant, dielectric constant, theelastic constants, the external magnetic field, and so on, are verifiedby analysising the physical model. The properties of the flexible METparts under low frequency are researched. Moreover, we choose PVDF(polyvinylidene fluoride) which has the best parameters aspiezoelectric polymer materials for piezoelectric phase, adopt stainless steel, aluminum, copper, polyimide polymer layer withplating copper film as elastic support respectively. By discussing themain affecting factors of the magnetoelectric coefficient ofdevice,the ME voltage coefficient frequency dependence of the METdevices with different elastic sheet were also investigated. As aresult, we obtained the best thickness ratio of piezoelectric andelastic sheet at low frequency, which can help us to design betterMET devices.According to the related curve, people can gain the biggestmagnetoelectric voltage conversion coefficient by choosing theoptimum elastic layer thickness. In conclusion, we provide powerfuldata analysis and theoretical support for the design of advanced METdevices in this thesis.