Controlling the cation distribution and electric polarization with epitaxial strain in Aurivillius-phase Bi5FeTi3O15

Abstract

This work explores the impact of in-plane bi-axial (epitaxial) strain on the cation distribution and electric polarization of the Aurivillius-phase compound Bi5FeTi3O15 using first-principles electronic structure calculations. Our calculations indicate that the site preference of the Fe 3+ cation can be controlled via epitaxial strain. Tensile strain enhances the preference for the inner sites within the perovskite-like layers of the Aurivillius-phase structure, whereas compressive strain favors occupation of the outer sites, i.e., the sites close to the Bi2O2 layer. Controlling the distribution of the magnetic cations offers the possibility to control magnetic order in this magnetically dilute system. Furthermore, the magnitude of the electric polarization is strongly strain-dependent, increasing under tensile strain and decreasing under compressive strain. We find strongly anomalous Born effective charges, both of the Bi 3+ and the Ti 4+ cations.Controlling the properties of complex transition metal oxides by epitaxial strain, i.e., by growing thin films of a certain material on a substrate with specific lattice mismatch, has emerged as a very efficient way for designing optimized functionalities. 1 In particular, the effect of epitaxial strain on the ferroelectric properties of perovskite materials is well studied, 2 and dramatic enhancements of polarization and ferroelectric ordering temperatures, 3 as well as emergence of ferroelectricity in otherwise nonpolar materials have been reported. 4,5 Recently, layered perovskite-related systems have come into focus as being potentially more amenable to developing polar lattice distortions compared to bulk perovskites. 6 Examples include artificial perovskite superlattices and double perovskites, as well as several families of naturally-layered perovskite-derived crystal structures such as the Ruddlesden-Popper series, Aurivillius-phases, or Dion-Jacobson systems. Only few studies addressing the strain response of these naturally-layered materials are currently available. Such studies are, however, of great interest due to the different mechanism underlying the ferroelectricity in these systems, which could lead to a different strain response compared to bulk perovskite ferroelectrics.Here we study the case of Bi 5 FeTi 3 O 15 (BFTO), 7,8 a representative of the family of naturally-layered Aurivillius-phases, which is of particular interest due to its potential multiferroic properties. 9 The crystal structure of the Aurivillius-phases consists of m perovskite layers (A m−1 B m O 3m+1 ) 2− stacked periodically along the [001] direction, and separated by fluorite-like (Bi 2 O 2 ) 2+ layers (see Fig. 1). 10,11 BFTO corresponds to the case with m = 4.A previous first-principles study of polarization-strain coupling in the m = 3 Aurivillius compound Bi 4 Ti 3 O 12 has shown a large response of in-plane polarization under bi-axial strain. 13 Apart from the introduction of an additional perovskite layer and the presence of the nominally non-ferroelectric Fe 3+ cation, an ...

Direct atomic scale determination of magnetic ion partition in a room temperature multiferroic material

“…These results indicate that site asymmetry is not a strong driver for cation partitioning in B6TFMO, leaving strain energy considerations 39 and electrostatic interactions as being the most likely mechanisms. Of these, the calculations of Birenbaum and Ederer 31 , 42 indicate that the strain energy factor is more important.…”

Buried In-Plane Ferroelectric Domains in Fe-Doped Single-Crystalline Aurivillius Thin Films

“…14,21 Incorporating magnetic dopants in the Aurivillius phases represents a potential route to induce magnetic properties to a performant ferroelectric material, thus creating a new multiferroic. Preliminary ab initio calculations 22,23 predicted that the epitaxial strain could play an important role in determining the distribution of magnetic dopants in the Aurivillius phase. Although in the last decade Aurivillius compounds exhibiting multiferroic properties have been reported -typically in the form of polycrystalline samples 9,17,20,[24][25][26][27][28][29][30] -the accurate description of the distribution of the magnetic ions at the base of the magnetic ordering has not yet been completely addressed in such an intricate system.…”

Composition dependence of the multifunctional properties of Nd-doped Bi4Ti3O12 ceramics

“…The Aurivillius family constitutes a class of compounds where new multiferroics with good ferroelectric and magnetic properties may be found [19][20][21]. As mentioned, Bi 4 Ti 3 O 12 has well-established high temperature ferroelectric properties [22,23], that can be enhanced by the substitution of Bi by Nd causing enlarged remnant polarization [24][25][26] accompanied by other changes of structural and physical properties [27][28][29][30][31].…”