Tuning the ferroelectric polarization in AA′MnWO₆double perovskites through A cation substitution

Abstract

Recent experimental and theoretical work has shown that the double perovskite NaLaMnWO 6 exhibits antiferromagnetic ordering owing to the Mn d states, and computational studies further predict it to exhibit a spontaneous electric polarization due to an improper mechanism for ferroelectricity [King et al., Phys. Rev. B, 2009, 79, 224428; Fukushima et al., Phys. Chem. Chem. Phys., 2011, 13, 12186], which make it a candidate multiferroic material. Using first-principles density functional calculations, we investigate nine isostructural and isovalent AA MnWO 6 double perovskites (A=Na, K, and Rb; A =La, Nd, and Y) with the aim of articulating crystal-chemistry guidelines describing how to enhance the magnitude of the electric polarization through chemical substitution of the A-site while retaining long-range magnetic order. We find that the electric polarization can be enhanced by up to 150% in compounds which maximize the difference in the ionic size of the A and A cations. By examining the tolerance factors, bond valences, and structural distortions (described by symmetry-adapted modes) of the nine compounds, we identify the atomic scale features that are strongly correlated with the ionic and electronic contributions to the electric polarization. We also find that each compound exhibits a purely electronic remnant polarization, even in the absence of a displacive polar mode. The analysis and design strategies presented here can be further extended to additional members of this family (B=Fe, Co, etc.), and the improper ferroelectric nature of the mechanism allows for the decoupling of magnetic and ferroelectric properties and the targeted design of novel multiferroics.

Atypical multiferroicity of HoCrO3 in bulk and film geometry

“…Recently, the appearance of FE order in a few members of RCrO 3 series has revived significant attention in this field. 6 For LuCrO 3 , the difference between T N and emergence of polar order as obtained from the pyroelectric current measurement is B80 K. 6,12 Analogous to this scenario, the onset of polar order has also been observed at around a B40 K higher temperature than T N for SmCrO 3 . [14][15][16] Recently, improper ferroelectricity has been argued in a few members of RCrO 3 where ferroelectricity is suggested to be driven by magnetic order.…”

Hybrid Improper Ferroelectricity in (Sr,Ca)3Sn2O7 and Beyond: Universal Relationship between Ferroelectric Transition Temperature and Tolerance Factor in n = 2 Ruddlesden–Popper Phases

“…This form of ferroelectricity should be prevalent in perovskiterelated materials because the octahedral rotations/tilts are ubiquitous structural distortions 21 (which are primarily of geometric origin and are driven by the size mismatch of the constituent ions). Indeed, a number of layered perovskites have been proposed as potential hybrid improper ferroelectrics through the integrated approach of symmetry arguments and first-principles calculations [22][23][24][25][26][27][28][29][30] , some of which have been experimentally confirmed to exhibit switchable polarization [31][32][33][34][35][36][37][38] , or at least crystalize in polar structures [39][40][41][42][43][44][45][46] . One can now utilize group theory to elucidate symmetry breaking caused by given distortions and identify whether their combinations result in a polar symmetry, and then the ferroelectricity.…”

Magneto-electric multiferroics: designing new materials from first-principles calculations

“…HIF is not restricted to 1/1 superlattices and to octahedral rotations and it has since 2008 been extended to (i) 2/2 superlattices involving identical A cations but two different B cations such as (YFeO3)2/(YTiO3)2 superlattices 131 ; (ii) thin film forms of oxides such as highly strained BiFeO3, PbTiO3, SrTiO3 or CaTiO3 98,99,132 ; (iii) hybrid organic-metal organic perovskites 133,134 ; (iv) double perovskite systems such as NaLaMnWO6 135 or RLaMnNiO6 136 (R=Lu-La, Y); (v) Jahn-Teller motions or anti-polar motions 98,99,[132][133][134][137][138][139][140] and (vi) other types of layered perovskites such as Ruddlesden-Popper 130,141,142 , Aurivilius 143 or Dion-Jacobson 144,145 (we invite the reader to Ref. 146 for a detailed discussions of these materials).…”