Magnetoelectricity in BiFeO 3 films: First-principles-based computations and phenomenology
Magnetoelectricity in BiFeO 3 films: First-principles-based computations and phenomenology
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DOI：
10.1103/physrevb.83.020102
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发表时间：
2011-01
影响因子：
3.7
通讯作者：
S. Prosandeev;I. Kornev;L. Bellaiche
中科院分区：
文献类型：
--
作者：
S. Prosandeev;I. Kornev;L. Bellaiche
用基于第一原理的有效哈密顿量计算了外延(001)BiFeO薄膜的线性和二次磁电系数。它的预测是在现象学模型中分析的，该模型提供了关于极化以及介电和磁化率的ME系数的解析表达式。它的主要发现是：(I)二次ME系数随着CC相内压缩应变的增加而显著增加，类似于先前报道的这些薄膜中线性ME系数的增强；(Ii)线性ME系数和二次ME系数的增强具有相同的宏观来源，即介电常数的增加；以及(Iii)从模拟中提取了两个不同的自由能项对总线性ME系数的相对贡献。这些解析表达式还有助于理解其他ME效应。
A first-principles-based effective Hamiltonian is used to compute linear and quadratic magnetoelectric (ME) coefficients in epitaxial (001) BiFeO${}_{3}$ thin films. Its predictions are analyzed within a phenomenological model that provides analytical expressions of the ME coefficients in terms of polarization, as well as dielectric and magnetic susceptibilities. Its main discoveries are: (i) the quadratic ME coefficient is dramatically enhanced by increasing the magnitude of the compressive strain within the Cc phase, similar to the previously reported enhancement of the linear ME coefficient in these films; (ii) the enhancements of the linear and quadratic ME coefficients have the same macroscopic origin, namely an increase in the dielectric permittivity; and (iii) the relative contribution of two different free-energy terms on the total linear ME coefficient is extracted from the simulations. The analytical expressions also help in understanding other ME effects.