Research On Giant Converse Magnetoelectric Coupling Characteristics Under Multi-physical Fields In Magnetoelectric Composite

The magnetoelectric composite has attracted extensive attention for its ferromagnetic and ferroelectric properties.Because the converse magnetoelectric effect of the magnetoelectric composite can alleviate the Joule heating of the Helmholtz coil and has the unique characteristics of electric field modulation magnetism and the sensitivity to reversion,it is widely used in various magnetoelectric devices,such as the electric write magnetic read memory devices and antennas.Thus,how to improve the performance of magnetoelectric devices by increasing the converse magnetoelectric coefficient becomes a major research hotspot.To date,although there are an increasing number of researches about the converse magnetoelectric coefficient,most of the researches only focused on the converse magnetoelectric effect under the single environment and neglected the magneto-mechanical-thermo-electric coupling effect of the converse magnetoelectric effect under the multi-physical fields,which includes bias magnetic field,temperature,pre-stress and electric field,etc.Thus,this paper will focus on the nonlinear magnetoelectric characteristics of the magnetoelectric composite under the multi-physical fields,analyze the factors that influence the converse magnetoelectric effect,and further explore how to realize the giant converse magnetoelectric effect.First,for the tri-layer symmetric magnetoelectric laminates,the analysis assumes the interfacial bonding between the layers is perfect,and according to the three-dimensional constitutive equations of the piezoelectric layer and magnetostrictive layer,a static converse magnetoelectric effect model considering the length ratio,width ratio and thickness ratio of the piezoelectric layer is obtained.Then the nonlinear magnetic parameters considering temperature,pre-stress and bias magnetic field in the magnetostrictive plate are calculated through introducing the nonlinear constitutive relations of the magnetostrictive plate,and then a nonlinear converse magnetoelectric coupling model considering the length ratio,width ratio and thickness ratio is established.The predictions of the model are in good agreement with the existing experimental results qualitatively and quantitatively.From the theoretical prediction results,it can be found that the static converse magnetoelectric effect decreases with the increasing length ratio.And when the length ratio is larger than a certain value,the thickness ratio of the piezoelectric layer should be increased or a pre-stress should be applied on the magnetostrictive layer to achieve the converse magnetoelectric effect along the length direction.The static converse magnetoelectric effect increases with the increasing width ratio.And when the width ratio is smaller,it is also necessary to increase the thickness ratio or apply a pre-stress on the magnetostrictive layer to achieve the converse magnetoelectric effect along the length direction.According to the above conclusions,under a group of volume ratios that the length ratio is lower and the width ratio is larger relatively,an optimal thickness ratio is predicted through the theoretical model.Finally,a set of optimal volume ratios are obtained.Under the optimal volume ratios,the converse magnetoelectric coefficient has increased to 6 times of the existing experimental value.Besides,based on the optimal volume ratios,the converse magnetoelectric effect under the different temperatures and stresses are further predicted.The research provides a theoretical basis for the shape design of the magnetoelectric laminated devices.Secondly,the resonant converse magnetoelectric coefficient is higher 1~2 orders than the converse magnetoelectric coefficient under the low-frequency condition.So,based on the equivalent circuit method,and introduced the new nonlinear magnetostrictive constitutive relations which not contain the inverse function,a nonlinear resonant magnetoelectric model considering the bias magnetic field,temperature and stress is established.The model is in agreement with the experimental result in qualitatively and quantitatively,which verified the validity of the model.And it is further explained the influence of the bias voltage on the resonant converse magnetoelectric effect,theoretically.The applied bias voltage is equivalent to a stress along the longitudinal direction of the magnetostrictive layer.From the theoretical predicted results,it can be seen that as the bias voltage changing from the positive voltage to the negative voltage,the resonant converse magnetoelectric coefficient decreases gradually in the low field and increases in the high field,shows a "flip" phenomenon.And the modulation of the bias voltage on the resonant converse magnetoelectric coefficient is more obvious with the increasing thickness ratio of the piezoelectric layer.Besides,the resonant converse magnetoelectric effect decreases as the ambient temperature increases under the specific bias magnetic field.For this phenomenon,applying an appropriate bias voltage can compensate the weakening effect of the temperature for the resonant converse magnetoelectric effect,and then the higher and more stable resonant converse magnetoelectric effect is achieved in a wide temperature range.Finally,in order to further improve the resonant converse magnetoelectric coefficient,the mechanical loss of the resonant converse magnetoelectric effect under the different bias magnetic fields,temperatures and input AC voltages is measured experimentally.First,the converse magnetoelectric coefficient of a tri-layer symmetric magnetoelectric composite versus frequency under the different bias magnetic fields is measured.Then according to the definition of the mechanical loss,the variation trend of the mechanical loss versus the bias magnetic field is obtained.A conclusion is showed as: the mechanical loss of the resonant converse magnetoelectric effect increases initially and then decreases with the increasing bias magnetic field.Changed the temperature and the input AC voltage,the mechanical loss increases and the corresponding resonant converse magnetoelectric coefficient gradually decreases with the increasing temperature.Compared the resonant converse magnetoelectric effect with the static converse magnetoelectric effect under the different temperatures,it can be concluded that with the increasing temperature,the decreasing piezomagnetic coefficient is not the unique reason led to the resonant converse magnetoelectric effect decreases,the increasing mechanical loss also can cause the resonant converse magnetoelectric effect decreases.And the mechanical loss increases with the increasing input AC voltage under the lower bias magnetic field,and the corresponding resonant converse magnetoelectric coefficient is decreased.But under the higher bias magnetic field,the input AC voltage has little effect on the mechanical loss and the resonant converse magnetoelectric coefficient.