菱形反铁磁体中的多铁性序参量。RCrO $_3$
Multiferroic order parameters in rhombic antiferromagnets. RCrO$_3$
摘要：
本文从对称性角度探讨了稀土正铬铁矿的磁电性。我们确定的主要结构序参量，并找到它们的耦合与铁电和磁有序。我们的计算表明，电偶极矩出现在附近的Cr3+离子在RCrO3的晶胞由于从其高度对称的位置在母体钙钛矿相（结构不稳定性）的氧离子的位移。发现RCrO_3的电偶极矩是以反铁电模式排列的，因此，RCrO_3本质上是反铁电材料。通过分类的序参量根据RCrO3对称群（D2H16）的不可约表示，我们确定了可能的扭曲，铁电和磁有序之间的耦合，并探讨新兴的磁电结构在这些方面。我们的分析使得有可能解释实验观察到的极化反转和随之而来的一系列的RCrO3化合物的自旋重新取向，并预测可能的情况下的相变RCrO3。
英文摘要：
In this paper, we explore magneteoelectricity of rare earth orthochromites from the symmetry point of view. We determine the principal structural order parameters and find their couplings with ferroelectric and magnetic orderings. Our calculations showed that electric dipole moments emerge in the vicinity of Cr3+ ions in the unit cell of RCrO3 due to the displacements of oxygen ions from their highly symmetric positions in the parent perovskite phase (structural instability). We find that the electric dipole moments are arranged in an antiferroelectric mode, so, in essence, RCrO3 are antiferroelectric materials. By classifying the order parameters according to the irreducible representations of the RCrO3 symmetry group (D2h16), we determine the possible couplings between distortive, ferroelectric and magnetic orderings and explore the emerging magnetoelectric structures in these terms. Our analysis makes it possible to explain experimentally observed polarization reversal and the concomitant reorientation of spins in a series of RCrO3 compounds and to predict the possible scenarios of phase transitions in RCrO3.
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