Enhanced hybrid improper ferroelectricity in Sr3−xBaxSn2O7 ceramics with a Ruddlesden–Popper (R–P) structure

Abstract

Hybrid improper ferroelectricity (HIF) has received increasing scientific attention since it provides great potential for realizing single phase room temperature multiferroicity with strong magnetoelectric coupling, and Ruddlesden–Popper (R–P) compounds AO(ABO3)n with even n are the most important candidates for HIFs. However, the modulation of ferroelectric polarization is recognized as a challenging issue. Here, Sr3−xBaxSn2O7 ceramics with a large remanent polarization with respect to other R–P HIFs (∼1.0 μC/cm2) combined with a reduced coercive field are reported. The polarization increases obviously with the increasing tolerance factor, inconsistent with the previous understanding. This is because the amplitude of tilt increases and rotation decreases, which results in the increased distortion of SnO6 octahedra. That is, the polarization of R–P compounds should be determined by the combined effects of tilting and rotation and not be simply evaluated by the tolerance factor.

A new electron diffraction approach for structure refinement applied to Ca3Mn2O7

“…We apply the D-LACBED technique to the Ruddlesden-Popper phase Ca 3 Mn 2 O 7 , which has attracted interest as a multiferroic (Benedek & Fennie, 2011;Fawcett et al, 1998) with the emergence of ferroelectric-ferromagnetic coupling occurring through the coupling of two non-polar modes with different symmetries. This effect has become known as hybrid improper ferroelectricity (Benedek & Fennie, 2011) and is currently being studied in a variety of related materials (Senn et al, 2015;Bansal et al, 2019;Xu et al, 2019;Chen et al, 2020).…”

Free-Carrier-Induced Ferroelectricity in Layered Perovskites

“…In this letter, we show that a particular group of ferroelectrics, the A 3 Sn 2 O 7 hybrid-improper ferroelectrics (HIFs) [35][36][37][38][39] behave differently, and their structural polarization is strongly enhanced by the free electrons introduced by chemical doping or electrostatic gating. This is related to an increase in the oxygen octahedral rotation angles induced by the added electrons in the parent perovskite compounds, which in turn leads to a larger structural polarization in these layered perovskite Ruddlesden-Popper (RP) phases [40].…”

“…While it is not always possible to order same charge cations in bulk, molecular beam epitaxy has been successfully used to obtain targeted chemical pressure in other RP phases (SrTiO 3 ) n (BaTiO 3 ) m SrO [57]. In Sr up to 10% of Ba ions are reported to preferentially substitute inequivalent Sr sites, however, the ordering tendencies depend sensitively on changes in the substitution amount [39]. We consider a structure where the 2/3 of Sr cations are substituted with Ba to form Ba 2 SrSn 2 O 7 , where the Ba cations are on the double-rocksalt layers of the RP structure, as shown in Fig.…”

Enhanced hybrid improper ferroelectricity in Fe/Nb cosubstituted Ca3Mn2O7 ceramics

“…Curie temperatures are obtained from the DSC measurements reported previously. 12,40,43,50 The linear fitting results are depicted by red dash lines with the critical τ value [Color figure can be viewed at wileyonlinelibrary.com] there are the rather simple antiparallel 180°-type domain configurations in Ca 3 [Mn 0.5 (Fe 0.5 Nb 0.5 ) 0.5 ] 2 O 7 , and this is similar to the situation in Ca 3 Ti 2 O 7 . [43][44][45] The previous work has also demonstrated that engineering the phase transition by chemical substitution is a useful method to modulate the domain configurations in ferroelectrics.…”

“…(C) Curie temperatures of n = 2 R‐P HIFs against the tolerance factors of their perovskite units. Curie temperatures are obtained from the DSC measurements reported previously 12,40,43,50 . The linear fitting results are depicted by red dash lines with the critical τ value [Color figure can be viewed at wileyonlinelibrary.com]…”