Symmetry Analysis of Magnetoelectric Effects in Perovskite-Based Multiferroics

Abstract

In this article, we performed symmetry analysis of perovskite-based multiferroics: bismuth ferrite (BiFeO3)-like, orthochromites (RCrO3), and Ruddlesden–Popper perovskites (Ca3Mn2O7-like), being the typical representatives of multiferroics of the trigonal, orthorhombic, and tetragonal crystal families, and we explored the effect of crystallographic distortions on magnetoelectric properties. We determined the principal order parameters for each of the considered structures and obtained their invariant combinations consistent with the particular symmetry. This approach allowed us to analyze the features of the magnetoelectric effect observed during structural phase transitions in BixR1−xFeO3 compounds and to show that the rare-earth sublattice has an impact on the linear magnetoelectric effect allowed by the symmetry of the new structure. It was shown that the magnetoelectric properties of orthochromites are attributed to the couplings between the magnetic and electric dipole moments arising near Cr3+ ions due to distortions linked with rotations and deformations of the CrO6 octahedra. For the first time, such a symmetry consideration was implemented in the analysis of the Ruddlesden–Popper structures, which demonstrates the possibility of realizing the magnetoelectric effect in the Ruddlesden–Popper phases containing magnetically active cations, and allows the estimation of the conditions required for its optimization.

Механизмы Магнитоэлектрических Эффектов В Оксидных Мультиферроиках С Прафазой Перовскита

“…Как было показано, в работах [29][30][31], в структурах с симметрией Pbnm при наличии магнитно-активных f -ионов (Gd, Dy, Tb), МЭЭ может возникнуть за счет антиферромагнитного (центро-асимметричного) упорядочения редкоземельных ионов, которое определяется антиферромагнитным вектором l редкоземельных ионов, компоненты которого классифицируются по неприводимым представлениям группы симметрии Pbnm (D 2h ) [33,34]. В случае замещения ионов Bi ионами La, как было показано в работе [25], магнитоэлектрические свойства Bi 1−x La x FeO 3 могут быть обусловлены квадратичным МЭЭ, что частично позволяет объяснить меньшую величину коэффициента МЭЭ, полученного в [28] по сравнению с экспериментальными значениями α МЕ [19].…”

Mechanisms of magnetoelectric effects in oxide multiferroics with a perovskite praphase

“…As shown in [29][30][31], in the presence of magnetically active f -ions (Gd, Dy, Tb) in structures with Pbnm symmetry, MEE can arise due to antiferromagnetic (centerasymmetric) ordering of rare-earth ions, which is determined by the antiferromagnetic vector l of the rare earth ions, whose components are classified by irreducible representations of the symmetry group Pbnm (D 2h ) [33,34]. In the case of replacement of Bi ions by La ions, as shown in [25], the magnetoelectric properties of Bi 1−x La x FeO 3 may be due to a quadratic MEE, which partially helps to explain the smaller value of the MEE coefficient obtained in [28] compared to the experimental values α ME [19].…”

“…As a result of RFeO 3 heat treatment or RCrO 3 electropolishing by an electric field, there is a decrease in symmetry to Pnma, in this case, the antiferroelectric structure of dipole moments is broken, which leads to the emergence of spontaneous electrical polarization and the emergence of MEE, which has been experimentally observed in work [35][36][37]. The MEE tensor can be calculated [31], using the table of irreducible representations of the Pnma group…”