Theory of low-frequency magnetoelectric coupling in magnetostrictive-piezoelectric bilayers
Theory of low-frequency magnetoelectric coupling in magnetostrictive-piezoelectric bilayers
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DOI：
10.1103/physrevb.68.054402
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发表时间：
2003-08-01
影响因子：
3.7
通讯作者：
Srinivasan, G
中科院分区：
文献类型：
--
作者：
Bichurin, MI;Petrov, VM;Srinivasan, G
提出了磁致伸缩和压电双层低频磁电 (ME) 效应的理论模型。为了考虑界面处的实际边界条件，提出了一种引入界面耦合参数 k 的新颖方法。平均方法用于估计有效材料参数。 ME 电压系数的表达式 alpha(E)(')=deltaE/deltaH，其中 deltaE 是外加交流磁场 deltaH 的感应电场，通过求解弹性静力学和静电方程获得。我们考虑未夹紧和刚性夹紧的双层以及三个不同的重要场方向：(i) 纵向场 (alpha(E,L)('))，其中极化场 E、偏置场 H 和交流场 deltaE 和 deltaH 都彼此平行并垂直于样品平面，(ii) 横向场 (alpha(E,T)('))，面内 H 和 deltaH 彼此平行并垂直于面外 E 和deltaE，以及 (iii) 面内纵向场 (alpha(E,IL)('))，所有场彼此平行并平行于样本平面。该理论预测，磁致伸缩相为钴铁氧体 (CFO)、铁氧体镍 (NFO) 或亚锰酸镧锶 (LSMO)，压电相为钛酸钡 (BTO) 或锆钛酸铅 (PZT)，双层会出现巨大的 ME 耦合。 α(E)(') 的估计是作为界面耦合 k 和压电相体积分数 nu 的函数进行的。在未钳位的样本中，alpha(E)(') 随着 k 的增加而增加。对于横向和纵向情况，最强的耦合发生在两相体积相等的情况下，但对于面内纵向情况，最大值出现在 nu=0.1 处。当夹住双层时，ME效应在纵向情况下增强，而在横向情况下减弱。该理论的其他重要结果如下。 (i) 面内纵向场的 ME 耦合预计最强，而（面外）纵向场的耦合最弱。 (ii) 在铁氧体基复合材料中，α(E,T)(') 和 α(E,IL)(') 比 α(E,L) 高 2-10 倍。 (iii) CFO-PZT 的 ME 电压系数预计最高，LSMO-PZT 的 ME 电压系数最低。本模型的结果与有关 alpha(E)(') 的体积和静磁场依赖性的可用数据进行了比较。通过比较，我们推断 NFO-PZT 的界面条件理想，而 CFO-PZT 和 LSMO-PZT 的界面耦合较差。
A theoretical model is presented for low-frequency magnetoelectric (ME) effects in bilayers of magnetostrictive and piezoelectric phases. A novel approach, the introduction of an interface coupling parameter k, is proposed for the consideration of actual boundary conditions at the interface. An averaging method is used to estimate effective material parameters. Expressions for ME voltage coefficients alpha(E)(')=deltaE/deltaH, where deltaE is the induced electric field for an applied ac magnetic field deltaH, are obtained by solving elastostatic and electrostatic equations. We consider both unclamped and rigidly clamped bilayers and three different field orientations of importance: (i) longitudinal fields (alpha(E,L)(')) in which the poling field E, bias field H, and ac fields deltaE and deltaH are all parallel to each other and perpendicular to the sample plane, (ii) transverse fields (alpha(E,T)(')) for in-plane H and deltaH parallel to each other and perpendicular to out-of-plane E and deltaE, and (iii) in-plane longitudinal fields (alpha(E,IL)(')) for all the fields parallel to each other and to the sample plane. The theory predicts a giant ME coupling for bilayers with cobalt ferrite (CFO), nickel ferrite (NFO), or lanthanum strontium manganite (LSMO) for the magnetostrictive phase and barium titanate (BTO) or lead zirconate titanate (PZT) for the piezoelectric phase. Estimates of alpha(E)(') are carried out as a function of the interface coupling k and volume fraction nu for the piezoelectric phase. In unclamped samples, alpha(E)(') increases with increasing k. The strongest coupling occurs for equal volume of the two phases for transverse and longitudinal cases, but a maximum occurs at nu=0.1 for the in-plane longitudinal case. Upon clamping the bilayer, the ME effect is strengthened for the longitudinal case and is weakened for the transverse case. Other important results of the theory are as follows. (i) The strongest ME coupling is expected for the in-plane longitudinal fields and the weakest coupling for the (out-of-plane) longitudinal case. (ii) In ferrite-based composites, alpha(E,T)(') and alpha(E,IL)(') are a factor of 2-10 higher than alpha(E,L). (iii) The highest ME voltage coefficients are expected for CFO-PZT and the lowest values are for LSMO-PZT. Results of the present model are compared with available data on the volume and static magnetic field dependence of alpha(E)('). We infer, from the comparison, ideal interface conditions in NFO-PZT and poor interface coupling for CFO-PZT and LSMO-PZT.