Cation distribution and magnetic structure of the ferrimagnetic spinel NiCO₂O₄

Research output: Contribution to journalArticle

Authors

  • JF Marco
  • JR Gancedo
  • M Gracia
  • JL Gautier
  • EI Rios
  • Frank Berry

Colleges, School and Institutes

Abstract

The compound NiCo2O4, with spinel-related structure, has been prepared by thermal decomposition of metal nitrates and its bulk structural properties examined by means of magnetic measurements, neutron diffraction, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The results suggest a delocalised electron distribution on the octahedral sites with average oxidation states of +3.5 and +2.5 for nickel and cobalt, respectively, and lead to a cation distribution for NiCo2O4 of {Ni0.13+Co0.92+}(tet)[Ni0.93.5+Co1.12.5+](oct)O-4. This electronic configuration is consistent with magnetisation measurements if applied magnetic fields cause a charge redistribution on the octahedral sites to favour Co3+ and Ni3+. The surface of NiCo2O4 was examined by X-ray photoelectron spectroscopy (XPS) and found to have a different composition containing Co2+, Co3+, Ni2+, Ni3+ and, probably, Ni4+.

Details

Original languageEnglish
Pages (from-to)3087-3093
Number of pages7
JournalJournal of Materials Chemistry
Volume11
Publication statusPublished - 1 Jan 2001