Topochemical Fluorination of La2NiO4+d: Unprecedented ordering of oxide and fluoride ions in La2NiO3F2

Research output: Contribution to journalArticlepeer-review

Authors

  • Kerstin Wissel
  • Jonas Heldt
  • Pedro Groszewics
  • Supratik Dasgupta
  • Hergen Breitzke
  • Manuel Donzelli
  • Aamir Waidha
  • Andrew Fortes
  • Jochen Rohrer
  • Gerd Buntkowsky
  • Oliver Clemens

Colleges, School and Institutes

External organisations

  • Institute of Materials Science, University of Stuttgart
  • Institute of Physical Chemistry, University of Stuttgart
  • Rutherford Appleton Laboratory

Abstract

The Ruddlesden–Popper (K2NiF4) type phase La2NiO3F2 was prepared via a polymer-based fluorination of La2NiO4+d. The compound was found to crystallize in the orthorhombic space group Cccm (a = 12.8350(4) Å, b = 5.7935(2) Å, c = 5.4864(2) Å). This structural distortion results from an ordered half occupation of the interstitial anion layers and has not been observed previously for K2NiF4-type oxyfluoride compounds. From a combination of neutron and X-ray powder diffraction and 19F magic-angle spinning NMR spectroscopy, it was found that the fluoride ions are only located on the apical anion sites, whereas the oxide ions are located on the interstitial sites. This ordering results in a weakening of the magnetic Ni–F–F–Ni superexchange interactions between the perovskite layers and a reduction of the antiferromagnetic ordering temperature to 49 K. Below 30 K, a small ferromagnetic component was found, which may be the result of a magnetic canting within the antiferromagnetic arrangement and will be the subject of a future low-temperature neutron diffraction study. Additionally, density functional theory-based calculations were performed to further investigate different anion ordering scenarios.

Details

Original languageEnglish
Pages (from-to)6549-6560
Number of pages12
JournalInorganic Chemistry
Volume57
Issue number11
Early online date11 May 2018
Publication statusPublished - 4 Jun 2018

Keywords

  • Oxyfluorides , Ruddlesden-Popper , Perovskites , Fluorination , La2NiO4+d , Magnetism