Iron(II,III) sulfide is a blue-black (sometimes pinkish) chemical compound of

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

and sulfur with formula Fe₃S₄ or FeS·Fe₂S₃, which is much similar to iron(II,III) oxide. It occurs naturally as the

sulfide mineral The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide (S22−) as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides, th ...

greigite Greigite is an iron sulfide mineral with the chemical formula . It is the sulfur equivalent of the iron oxide magnetite (Fe3O4). It was first described in 1964 for an occurrence in San Bernardino County, California, and named after the mineralogis ...

and is magnetic. It is a bio-mineral produced by and found in

magnetotactic bacteria Magnetotactic bacteria (or MTB) are a polyphyletic group of bacteria that orient themselves along the magnetic field lines of Earth's magnetic field. Discovered in 1963 by Salvatore Bellini and rediscovered in 1975 by Richard Blakemore, this ali ...

. It is a

mixed valence compound Mixed valence complexes contain an element which is present in more than one oxidation state. Well-known mixed valence compounds include the Creutz–Taube complex, Prussian blue, and molybdenum blue. Many solids are mixed-valency including ...

, featuring both Fe²⁺ and Fe³⁺ centers, in 1:2 ratio.

Crystal structure

The crystallographic unit cell is cubic, with

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...

Fd3m. The S anions form a cubic close-packed lattice, and the Fe cations occupy both tetrahedral and octahedral sites.Vaughan, D. J.; Craig, J. R. “Mineral Chemistry of Metal Sulfides" Cambridge University Press, Cambridge: 1978. .

Magnetic and electronic properties

Like the related oxide

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With th ...

(Fe₃O₄), iron(II,III) sulfide is

ferrimagnetic A ferrimagnetic material is a material that has populations of atoms with opposing magnetic moments, as in antiferromagnetism, but these moments are unequal in magnitude so a spontaneous magnetization remains. This can for example occur when ...

, with the spin magnetic moments of the centers in the tetrahedral sites oriented in the opposite direction as those in the octahedral sites, and a net magnetization. Both metal sites have high spin quantum numbers. The electronic structure of greigite is that of a half metal.

Crystal structure

Magnetic and electronic properties

References

Further reading