DOE OSTI2020
CoFe2O4 is Spinel-like structured and crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are six inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six FeO6 octahedra and corners with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 54–60°. There are a spread of Fe–O bond distances ranging from 1.89–1.97 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra, edges with two equivalent FeO6 octahedra, and edges with four CoO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.04–2.07 Å. In the third Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six FeO6 octahedra and corners with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 54–60°. There are a spread of Fe–O bond distances ranging from 1.89–1.97 Å. In the fourth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra, edges with two equivalent FeO6 octahedra, and edges with four CoO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.98–2.03 Å. In the fifth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six FeO6 octahedra and corners with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 54–60°. There are a spread of Fe–O bond distances ranging from 1.90–1.94 Å. In the sixth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra, edges with two equivalent FeO6 octahedra, and edges with four CoO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.02–2.06 Å. There are four inequivalent Co2+ sites. In the first Co2+ site, Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six FeO4 tetrahedra, edges with two CoO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Co–O bond distances ranging from 2.07–2.12 Å. In the second Co2+ site, Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six equivalent FeO4 tetrahedra, edges with two equivalent CoO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Co–O bond distances ranging from 2.07–2.11 Å. In the third Co2+ site, Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six FeO4 tetrahedra, edges with two CoO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Co–O bond distances ranging from 2.08–2.13 Å. In the fourth Co2+ site, Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six FeO4 tetrahedra, edges with two equivalent CoO6 octahedra, and edges with four equivalent FeO6 octahedra. There are a spread of Co–O bond distances ranging from 2.04–2.10 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Fe3+ and two Co2+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Fe3+ and two Co2+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Co2+ atom. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Co2+ atom. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Co2+ atom. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Fe3+ and two Co2+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Co2+ atom. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Fe3+ and two Co2+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Co2+ atom. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Fe3+ and two Co2+ atoms. In the eleventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe3+ and one Co2+ atom. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Fe3+ and two Co2+ atoms.