The Verwey transition is a low-temperature

phase transition In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states of ...

in the mineral

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 ...

associated with changes in its magnetic, electrical, and thermal properties. It typically occurs near a temperature of 120 K but is observed at a range of temperatures between 80 and 125 K, although the

spread Spread may refer to: Places * Spread, West Virginia Arts, entertainment, and media * ''Spread'' (film), a 2009 film. * ''$pread'', a quarterly magazine by and for sex workers * "Spread", a song by OutKast from their 2003 album ''Speakerboxxx/T ...

is generally tight around 118-120 K in natural magnetites. Upon warming through the Verwey transition temperature (), the magnetite crystal lattice changes from a monoclinic structure insulator to the metallic cubic inverse spinel structure that persists at room temperature. The phenomenon is named after Evert Verwey, a Dutch chemist who first recognized, in the 1940s, the connection between the structural transition and the changes in the physical properties of magnetite. This was the first metal-insulator transition to be found. The Verwey transition is near in temperature, but distinct from, a magnetic isotropic point in magnetite, at which the first

magnetocrystalline anisotropy In physics, a ferromagnetic material is said to have magnetocrystalline anisotropy if it takes more energy to magnetize it in certain directions than in others. These directions are usually related to the principal axes of its crystal lattice. I ...

constant changes sign from positive to negative. The temperature and physical expression of the Verwey transition are highly sensitive to the stress state of magnetite and the stoichiometry. Non-stoichiometry in the form of metal

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

substitution or partial

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

can lower the transition temperature or suppress it entirely.

References

{{reflist Phase transitions Paleomagnetism Rock magnetism Magnetism

See also

References