Statistical Theory of Magnetoelectric Effects in Antiferromagnetics
Statistical Theory of Magnetoelectric Effects in Antiferromagnetics
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反铁磁学中磁电效应的统计理论
DOI：
10.1103/physrev.128.2546
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发表时间：
1962
期刊：
影响因子：
--
通讯作者：
G. Rado
中科院分区：
文献类型：
--
作者：
G. Rado
根据包含分子场近似和自由能的统计力学计算表明，作者先前提出的自旋-轨道机制不仅导致电感应效应，而且还导致磁感应磁电效应。此外，这一机制被发现导致了磁电对电极化率的贡献。对于两个亚晶格的反铁磁体，磁电极化率的温度依赖关系与前人在唯象基础上预测的磁电极化率在数量上不同，但在性质上相似。尽管即使是纯磁性数据也表明，双亚晶格模型不能严格适用于{\mathm{Cr}}_{2}${\mathm{O}}_{3}$，但将本理论与实验进行比较发现(借助于红宝石中某些顺磁共振谱线的电场分裂数据)，自旋-轨道机制是在${\mathm{Cr}}_{2}$${\mathm{O}}_{3}$中观察到的磁电效应的重要组成部分。该附录包含了一些与磁电效应有关的已知热力学关系的修正推导。它还包含一个基于热力学和对称性考虑的建议，即可能存在“压磁”和“旋电”效应。
It is shown on the basis of a statistical mechanical calculation involving the molecular field approximation and the free energy that the spin-orbit mechanism previously proposed by the author leads not only to the electrically induced but also to the magnetically induced magnetoelectric effect. In addition, this mechanism is found to lead to a magnetoelectric contribution to the electric susceptibility. For a two-sublattice antiferromagnet, the temperature dependence of the magnetoelectric susceptibilities is shown to be quantitatively different from but qualitatively similar to that predicted in the previous work on a phenomenological basis. Although even purely magnetic data indicate that a two-sublattice model is not strictly applicable to ${\mathrm{Cr}}_{2}$${\mathrm{O}}_{3}$, a comparison of the present theory with experiments suggests (with the help of data on the electric field splitting of certain paramagnetic resonance lines in ruby) that the spin-orbit mechanism accounts for a significant part of the magnetoelectric effects observed in ${\mathrm{Cr}}_{2}$${\mathrm{O}}_{3}$. The Appendix contains a revised derivation of some known thermodynamic relations relevant to magnetoelectric effects. It also contains a proposal, based on thermodynamic and symmetry considerations, that "piezomagnetoelectric" and "gyroelectric" effects may exist.