Bi2CoO2F4-A Polar, Ferrimagnetic Aurivillius Oxide-Fluoride

Euan A S Scott; Eleni Mitoudi Vagourdi; Mats Johnsson; Vanessa Cascos; Filbin John; Dave Pickup; Alan V Chadwick; Hania Djani; Eric Bousquet; Weiguo Zhang; P Shiv Halasyamani; Emma E McCabe

doi:10.1021/acs.chemmater.2c02745

Bi₂CoO₂F₄-A Polar, Ferrimagnetic Aurivillius Oxide-Fluoride

Chem Mater. 2022 Nov 8;34(21):9775-9785. doi: 10.1021/acs.chemmater.2c02745. Epub 2022 Oct 17.

Authors

Affiliations

¹ School of Physical Sciences, University of Kent, Kent, Canterbury CT2 7NH, U.K.
² Department of Materials and Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden.
³ Centre de Développement des Technologies Avancées, cité 20 aout 1956, Baba Hassan, Alger 16081, Algeria.
⁴ Theoretical Materials Physics, Q-MAT, CESAM, Université de Liège, Allée 6 août, 17, B-4000, Sart Tilman, Liège 4000, Belgium.
⁵ Department of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204, United States.
⁶ Department of Physics, Durham University, South Road, Durham DH1 3LE, U.K.

Abstract

Aurivillius oxides have been a research focus due to their ferroelectric properties, but by replacing oxide ions by fluoride, divalent magnetic cations can be introduced, giving Bi₂ MO₂F₄ (M = Fe, Co, and Ni). Our combined experimental and computational study on Bi₂CoO₂F₄ indicates a low-temperature polar structure of P2₁ ab symmetry (analogous to ferroelectric Bi₂WO₆) and a ferrimagnetic ground state. These results highlight the potential of Aurivillius oxide-fluorides for multiferroic properties. Our research has also revealed some challenges associated with the reduced tendency for polar displacements in the more ionic fluoride-based systems.