Tetrataenite is a

native metal A native metal is any metal that is found pure in its metallic form in nature. Metals that can be found as native deposits singly or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, manganese, m ...

alloy 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 Taenite is a mineral found naturally on Earth mostly in iron meteorites. It is an alloy of iron and nickel, with a chemical formula of and nickel proportions of 20% up to 65%. The name is derived from the Greek ταινία for "band, ribbon" ...

. It is one of the mineral phases found in

meteoric iron Meteoric iron, sometimes meteoritic iron, is a native metal and early-universe protoplanetary-disk remnant found in meteorites and made from the elements iron and nickel, mainly in the form of the mineral phases kamacite and taenite. Meteoric ir ...

.Mindat.org – Tetrataenite
/ref>''Handbook of Mineralogy'' – Tetrataenite
/ref>

Formation

Tetrataenite forms naturally in

iron meteorite Iron meteorites, also known as siderites, or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most iron met ...

s that contain

that are slow-cooled at a rate of a few degrees per million years, which allows for ordering of the Fe and Ni atoms. It is found most abundantly in slow-cooled

chondrite A chondrite is a stony (non-metallic) meteorite that has not been modified, by either melting or differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primi ...

meteorites, as well as in

mesosiderite Mesosiderites are a class of stony–iron meteorites consisting of about equal parts of metallic nickel-iron and silicate. They are breccias with an irregular texture; silicates and metal occur often in lumps or pebbles as well as in fine-grained ...

s. At high (as much as 52%) Ni content and temperatures below 320 °C (the order-disorder transition temperature), tetrataenite is broken down from

and distorts its face centered cubic crystal structure to form the

tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square ...

L1₀ structure."Taenite." ''Britannica Academic'', Encyclopædia Britannica, 6 Nov. 2009. academic-eb-com.ezproxy.neu.edu/levels/collegiate/article/taenite/342903. Accessed 30 Mar. 2018. The L1₀ phase can be synthetically produced by

neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...

- or electron-irradiation of FeNi below 593 K, by hydrogen-reduction of nanometric NiFe₂O₄, or by crystallization of Fe-Ni alloys in the presence of traces of phosphorus. In 2015, it was reported that tetrataenite was found in a terrestrial rock – a

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 the ...

body from the Indo-Myanmar ranges of northeast India.

A laboratory protocol for bulk synthesis, announced in 2022

Mixing iron, nickel and phosphorus together in specific quantities and smelting the mixture forms tetrataenite in bulk quantities, in seconds. This discovery, announced in 2022, raises hopes that some of the technologies which currently require the use of

magnetic alloys A magnetic alloy is a combination of various metals from the periodic table such as ferrite that contains at least one of the three main magnetic elements: iron (Fe), nickel (Ni), or cobalt (Co) etc.. Such an alloy must contain but is not limit ...

containing rare earths metals may be achievable using magnets made of tetrataenite as an alternative, which would reduce dependence on toxic, environmentally harmful rare earth mines controlled largely by the Chinese government.

Crystal structure

Tetrataenite has a highly ordered crystal structure, appearing creamy in color and displaying

optical anisotropy Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefring ...

. Its appearance is distinguishable from taenite, which is dark gray with low

reflectivity The reflectance of the surface of a material is its effectiveness in Reflection (physics), reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the respon ...

. FeNi easily forms into a cubic crystal structure, but does not have

magnetic anisotropy In condensed matter physics, magnetic anisotropy describes how an object's magnetic properties can be different depending on direction. In the simplest case, there is no preferential direction for an object's magnetic moment. It will respond to ...

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 Coercivity, also called the magnetic coercivity, coercive field or coercive force, is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized. Coercivity is usually measured in ...

. 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 permanent magnets such as

samarium Samarium is a chemical element with symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of samar ...

and

neodymium Neodymium is a chemical element with the symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth metals. It is a hard, slightly malleable, silvery metal that quickly tarnishes i ...

since both

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

and

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

are earth-abundant and inexpensive.

References