LiNbO3-type InFeO3: Room-temperature polar magnet without second-order Jahn-Teller active ions

K. Fujita (1) , T. Kawamoto (1) , I. Yamada (2) , O. Hernandez (3) , N. Hayashi (4) , H. Akamatsu (5) , W. Lafargue-Dit-Hauret (3) , X. Rocquefelte (3) , M. Fukuzumi (6) , P. Manuel (7) , A.J. Studer (8) , C.S. Knee (9) , K. Tanaka (1)

1 Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
2 Department of Energy Systems Eng., Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
3 ISCR - Institut des Sciences Chimiques de Rennes
4 Research Institute for Production Development [Kyoto]
5 Penn State - Pennsylvania State University
6 Hyogo Prefectural Institute of Technology
7 RAL - STFC Rutherford Appleton Laboratory
8 ANSTO - Australian Nuclear Science and Technology Organisation [Australie]
9 GU - University of Gothenburg

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 AFeO3 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+ (d10) and Fe3+ (d5) 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 d0 transition-metal ions and/or 6s2 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 μC/cm2 along the c-axis, comparable to that of an isostructural and SOJT-active perovskite ferroelectric, BiFeO3 (90-100 μC/cm2). Magnetic studies demonstrate weak ferromagnetic behavior at room temperature, as a result of the canted G-type antiferromagnetic ordering of Fe3+ moments below TN ∼ 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. © 2016 American Chemical Society.

Keywords: Antiferromagnetism; Barium compounds; Bismuth compounds; Ferroelectric materials; Iron compounds; Jahn-Teller effect; Magnets; Metal ions; Metals; Perovskite; Polarization; Positive ions; Transition metal compounds; Transition metals; Antiferromagnetic orderings; Electric polarization; Elevated temperature; Ferromagnetic behaviors; Magnetic studies; Orthorhombic perovskite; Polar structures; Structure analysis; Density functional theory

Domains: Chemical Sciences; Chemical Sciences; Material chemistry

K. Fujita, T. Kawamoto, I. Yamada, O. Hernandez, N. Hayashi, et al.. LiNbO3-type InFeO3: Room-temperature polar magnet without second-order Jahn-Teller active ions. Chemistry of Materials, 2016, 28 (18), pp.6644--6655. ⟨10.1021/acs.chemmater.6b02783⟩. ⟨hal-01381124⟩