Magnetite (inverse spinel) Fe₃O₄

Unit cell

Lattice constants

a = 8.396 Å, b = 8.396 Å, c = 8.396 Å; α = 90°, β = 90°, γ = 90°

Cell volume

591.9 ų

Atoms in the cell

56 (Fe 24, O 32)

Formula units Z

8

Calculated density

5.20 g cm⁻³

Shortest contact

1.876 Å

Coordination

Fe³⁺ (tet)

CN 4 at 1.88 Å (4 O)

Fe²⁺/Fe³⁺ (oct)

CN 6 at 2.07 Å (6 O)

O

CN 4 at 1.88 Å (4 Fe)

About the structure

• The same framework as spinel, but with the cations swapped round: the tetrahedral (8a) sites hold Fe³⁺, and the octahedral (16d) sites hold Fe²⁺ and Fe³⁺ in equal numbers — an inverse spinel, written Fe³⁺[Fe²⁺Fe³⁺]O₄.
• Coordination: Fe(tet) 4, Fe(oct) 6, O 4.
• Fast electron hopping between Fe²⁺ and Fe³⁺ on the octahedral sites makes magnetite a conductor and a ferrimagnet (lodestone).
• Mg₂TiO₄, NiFe₂O₄ and CoFe₂O₄ are also inverse; MgAl₂O₄ and ZnFe₂O₄ are normal.

Atom positions (fractional, one cell)

Z, coordination numbers, distances, density and packing on this page are computed from these coordinates.