Abstrakt
Magnetite represents a prototype compound with a mixed valence of iron cations. Its structure and electron ordering below the Verwey transition have been studied for decades.
A recently published precise crystallographic structure [Senn et al., Nature (London) 481, 173 (2012)] accompanied by a suggestion of a "trimeron" model has given a new impulse to magnetite research. Here we investigate hyperfine field anisotropy in the Cc phase of magnetite by quantitative reanalysis of published measurements of the dependences of the Fe-57 nuclear magnetic resonance frequencies on the external magnetic field direction.
Further, ab initio density-functional-theory-based calculations of hyperfine field depending on the magnetization direction using the recently reported crystal structure are carried out, and analogous hyperfine anisotropy data linked to particular crystallographic sites are determined. These two sets of data are compared, and mutually matching groups of the iron B sites in the 8: 5: 3 ratio are found.
Moreover, information on electronic structure is obtained from the ab initio calculations. Our results are compared with the trimeron model and with an alternative analysis [Patterson, Phys.
Rev. B 90, 075134 (2014)] as well.