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LiNbO3-Type InFeO3: Room-Temperature Polar Magnet without Second-Order Jahn-Teller Active Ions

K. Fujita ; T. Kawamoto ; I. Yamada ; O. Hernandez ; N. Hayashi ; H. Akamatsu ; W. Lafargue-Dit-Hauret ; X. Rocquefelte ; M. Fukuzumi ; P. Manuel ; A. J. Studer ; Christopher S Knee (Institutionen för kemi och kemiteknik, Oorganisk miljökemi) ; K. Tanaka
Chemistry of Materials (0897-4756). Vol. 28 (2016), 18, p. 6644-6655.
[Artikel, refereegranskad vetenskaplig]

Great effort has been devoted to developing single-phase magnetoelectric multiferroics, but room-temperature coexistence of large electric polarization and magnetic ordering still remains elusive. Our recent finding shows that such polar magnets can be synthesized in small-tolerance-factor perovskites AFeO(3) with unusually small cations at the A-sites, which are regarded as having a LiNbO3-type structure (space group R3c). Herein, we experimentally reinforce this finding by preparing a novel room-temperature polar magnet, LiNbO3-type InFeO3. This compound is obtained as a metastable quench product from an orthorhombic perovskite phase stabilized at 15 GPa and an elevated temperature. The structure analyses reveal that the polar structure is characterized by displacements of In3+ (d(10)) and Fe3+ (d(5)) ions along the hexagonal c-axis (pseudocubic [111] axis) from their centrosymmetric positions, in contrast to well-known perovskite ferroelectrics (e.g., BaTiO3, PbTiO3, and BiFeO3) where d(0) transition-metal ions and/or 6s(2) lone-pair cations undergo polar displacements through the so-called second-order Jahn-Teller (SOJT) distortions. Using density functional theory calculations, the electric polarization of LiNbO3-type InFeO3 is estimated to be 96 mu C/cm(2) along the c-axis, comparable to that of an isostructural and SOJT-active perovskite ferroelectric, BiFeO3 (90-100 mu C/cm(2)). Magnetic studies demonstrate weak ferromagnetic behavior at room temperature, as a result of the canted G-type antiferromagnetic ordering of Fe3+ moments below T-N similar to 545 K. The present work shows the functional versatility of small-tolerance-factor perovskites and provides a useful guide for the synthesis and design of room-temperature polar magnets.

Denna post skapades 2016-11-11.
CPL Pubid: 245066


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