Abstract: The influence of rotomagnetic (RM), rotoelectric (RE) and magnetoelectric (ME) coupling on phase diagram and properties of antiferrodistortive (AFD) perovskite oxides was reviewed. The main examples we consider in the review are typical AFD perovskites, such as incipient ferroelectrics EuTiO3, SrTiO3, EuxSr1-xTiO3, multiferroic BiFeO3 and Bi1-xRxFeO3 (x = La, Nd). The strong influence of RM, RE and ME couplings on the physical properties and phase diagrams including antiferromagnetic (AFM), ferroelectric (FE) and structural AFD phases has been revealed in the framework of Landau-Ginzburg-Devonshire (LGD) theory, as well as the prediction of novel (double and triple) multiferroic phases has been demonstrated.
In the review we are especially focused on:
(a) the possibility to induce FM (FE) phase in EuTiO3 (as well as in other paraelectric AFM oxides) by the application of an electric (magnetic) field due to the ME coupling;
(b) the analysis of the size effects and novel phases in EuxSr1-xTiO3 nanosystems, where the LGD theory predicts the presence of the triple AFD-FE-FM(AFM) phase at low temperatures;
(c) the appearance of improper spontaneous polarization and pyroelectricity in the vicinity of antiphase domain boundaries, structural twin walls, surfaces and interphases in the AFD phase of non-ferroelectric SrTiO3 induced by the flexoelectricity and rotostriction;
(d) the occurrence of low symmetry monoclinic phase with in-plane FE polarization in thin strained EuxSr1-xTiO3 films and its stabilization over wide temperature range by AFD oxygen octahedra tilts due to flexoelectric and rotostriction coupling;
(e) discussion of a surprisingly strong size-induced increase of AFM transition temperature caused by the joint action of RM coupling with elastic stress accumulated in the intergrain spaces of BiFeO3 dense ceramics.
Noteworthy, the results obtained within LGD approach show the possibility of controlling multiferroicity, including FE, FM and AFM phases in bulk and nanosized AFD ferroics, with the help of size effects and/or electric/magnetic field application. Since theoretical results are in qualitative agreement with experimental results, we conclude that LGD theory can be successfully applied to many AFD perovskite oxides.
Title: Anomalies of phase diagrams and physical properties of antiferrodistortive perovskite oxides
DOI: https://doi.org/10.1016/j.jallcom.2018.11.015 Journal of Alloys and Compounds (2019) 778, 452-479
Postprint deposited in the repository: https://arxiv.org/abs/1807.01743