Coupling of the local defect and magnetic structure of Wüstite, Fe1–xO
P J Saines, M G Tucker, D A Keen, A K Cheetham and A L Goodwin
Phys Rev B 88, 134418 (2013)
The final authors’ version of this article is available open access via. arXiv.org.
The local nuclear and magnetic structure of wüstite, Fe1−xO, and the coupling between them, have been examined using reverse Monte Carlo refinements of variable-temperature neutron total scattering data. The results from this analysis suggest that the individual units in a tetrahedral defect cluster are connected along 〈110〉 vectors into a Koch-Cohen-like arrangement, with the majority of octahedral vacancies concentrated near these defects. Bond valence calculations indicate a change in the charge distribution on the cations with the charge on the tetrahedral interstitials increasing on cooling. The magnetic structure is more complex than previously thought, corresponding to a noncollinear spin arrangement described by a superposition of a condensed spin wave on the established type-II antiferromagnetic ordering. This leads to an architecture with four groups of cations, each with different spin directions. The cations within the interstitial clusters appear to be weakly ferromagnetically coupled, and their spins are correlated to the spins of the octahedral cations closest to them. This work not only provides further insight into the local structure of wüstite but also enables a better understanding of the coupling between defect structures and magnetic and charge ordering in complex materials.