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= Tetrataenite = Tetrataenite is a native metal composed of chemically-ordered L10-type FeNi, recognized as a mineral in 1980. The mineral is named after its tetragonal crystal structure and its relation to the iron-nickel alloy, taenite. It is one of the mineral phases found in meteoric iron.

Meteorites
Tetrataenite forms naturally in slow-cooled iron meteorites that contain taenite. It is found most abundantly in slow-cooled chondrite meteorites (below 350 °C), as well as in mesosiderites. At high (as much as 52%) Ni content and temperatures below 300 °C, tetrataenite is broken down from taenite in meteorites. The tetragonal L10 structure forms through a disorder-order transformation from the A1 face centered cubic (fcc) crystal structure of FeNi.

Terrestrial Synthesization
Thin films of FeNi alloys have been created with sputter deposition followed by annealing and confirmed to be L10 structure.

Crystal Structure
Tetrataenite has a highly ordered crystal structure, appearing creamy in color and displaying optical anisotropy. FeNi easily forms into a cubic crystal structure, but does not have magnetic anisotropy in this form. Three variants of the L10 tetragonal crystal structure have been found, as chemical ordering can occur along any of the three axes.

Magnetic Properties
Tetrataenite displays permanent magnetization, in particular, high coercivity. It has a theoretical magnetic energy product, the maximum amount of magnetic energy stored, over 335 kJ m-3.

Applications
Tetrataenite is a candidate for replacing rare-earth magnet s such as samarium and neodymium since both iron and nickel are earth-abundant and inexpensive.