NMR Study of the Low Temperature Phase of Fe₃O₄. II. Electron Ordering Analysis

Abstract

The number of the inequivalent octahedral sites on which Fe 3+ ions are located and the values of the anisotropic internal fields of the ions were determined in the preceding paper. From these results and under the several assumptions, the electron ordering schemes on the (001) planes were determined completely. There remains some ambiguity on the way of piling up these c -planes along the c -axis. The proposed electron ordering scheme is as follows. Along the a -axis a pair of Fe 2+ ions and a pair of Fe 3+ ions line up alternately. Along the b -axis a group of three Fe 3+ ions and one Fe 2+ ion or a group of three Fe 2+ ions and one Fe 3+ ion line up alternately. This electron ordering may be caused by the pairing of Fe 2+ ions along the a -axis as well as the short range ordering due to the electrostatic energy. The new model is quite promising but the NMR study at the present stage still cannot eliminate other electron orderings, e.g. , Fe 2+ ion and Fe 3+ ion align alternately along the a - and b -axes.