Verwey transition
The Verwey transition is a low-temperature phase transition in the mineral magnetite associated with changes in its magnetic, electrical, and thermal properties.[1] 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 is generally tight around 118-120 K in natural magnetites.[1][2] Upon warming through the Verwey transition temperature (TV), the magnetite crystal lattice changes from a monoclinic structure insulator to the metallic cubic inverse spinel structure that persists at room temperature.[3] 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.[4]
The Verwey transition is near in temperature, but distinct from, a magnetic isotropic point in magnetite, at which the first magnetocrystalline anisotropy constant changes sign from positive to negative.[5]
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 substitution or partial oxidation can lower the transition temperature or suppress it entirely.[5][6]
See also
- Morin transition – Magnetic phase transition in α-Fe2O3 hematite
References
- ^ a b Walz, Friedrich (15 March 2002). "The Verwey transition - a topical review". Journal of Physics: Condensed Matter. 14 (12): R285–R340. doi:10.1088/0953-8984/14/12/203. S2CID 250773238.
- ^ Jackson, M.J.; Moskowitz, B. (2021). "On the distribution of Verwey transition temperatures in natural magnetites". Geophysical Journal International. 224 (2): 1314–1325. doi:10.1093/gji/ggaa516.
- ^ Kosterov, Andrei (2007). "Magnetic properties, low-temperature". In Gubbins, David; Herrero-Bervera, Emilio (eds.). Encyclopedia of geomagnetism and paleomagnetism. Dordrecht: Springer. pp. 515–525. ISBN 9781402044236.
- ^ Miller, Sandi (19 March 2020). "Dancing electrons solve a longstanding puzzle in the oldest magnetic material". Space Daily. Archived from the original on 21 March 2020. Retrieved 2 September 2021.
- ^ a b Aragón, Ricardo; Buttrey, Douglas J.; Shepherd, John P.; Honig, Jurgen M. (1 January 1985). "Influence of nonstoichiometry on the Verwey transition". Physical Review B. 31 (1): 430–436. Bibcode:1985PhRvB..31..430A. doi:10.1103/PhysRevB.31.430. PMID 9935445.
- ^ Özdemir, Özden; Dunlop, David J.; Moskowitz, Bruce M. (20 August 1993). "The effect of oxidation on the Verwey transition in magnetite". Geophysical Research Letters. 20 (16): 1671–1674. Bibcode:1993GeoRL..20.1671O. doi:10.1029/93GL01483. hdl:11299/175055.