磁电双层膜层间耦合的弹性力学研究

Elastomechanical study of interface coupling in magnetoelectric bilayers

基于磁致伸缩相与压电相的本构方程,应用弹性力学模型,简要介绍了如何推导自由状态的磁电双层膜纵向、横向磁电(ME)电压系数.并采用相应的材料参数计算了La0.7Sr0.3MnO3-Pb(Zr,Ti)O3(LSMO-PZT),Tb1-xDyxFe2-y(TDF)-PZT双层膜中的磁电电压系数,具体分析了其与压电相的体积分数v、界面耦合参数k以及偏置磁场H之间的关系.分析结果表明,在某一体积分数vm下,ME电压系数达到最大值,且最大值与k成近似线性关系.由于TDF的超大磁致伸缩效应,TDF-PZT双层膜的横向ME电压系数可达1.9Vcm-1Oe-1,而LSMO-PZT的仅为165mVcm-1Oe-1(1Oe=80A/m).将LSMO-PZT中横向ME电压系数随偏置磁场H变化的理论值与实验结果进行对照,其界面耦合参数k为0.2.研究结果表明:优异的磁致伸缩性能、合适的体积分数、良好的界面耦合是影响ME效应的关键因素.

A theoretical model is introduced to derive the ME voltage coefficients of bilayer in free state according to the constitutive equations of magnetostrictive and piezoelectric phases. Using this model, the ME voltage coefficients of La0.7 Sr0.3 MnO3 （LSMO）- PZT and Tb1-xDyxFe2-y （TDF）-PZT bilayers have been calculated and analyzed using the corresponding material parameters of individual phases. The results show that the ME voltage coefficient increases to a maximum at a given volume fraction of piezoelectric phase. With increasing interface coupling parameter k, an approximately linear increase of the maximum ME voltage coefficient have been observed. The maximum ME voltage coefficient for TDF-PZT bilayer reaches 1.9 Vcm^-1Oe^-1, while for LSMO-PZT bilayer, the maximum value is only 165 mVcm^-1 Oe^-1 . The theoretical results of ME voltage coefficients versus bias magnetic field for LSMO-PZT bilayer have been found to agree well with the measured data when k = 0.2. Analysis shows that large magnetostriction, appropriate volume fraction and adequate interface coupling are key facters for obtaining excellent ME performance.