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At low temperatures, magnetite undergoes a crystal structure phase transition from a monoclinic structure to a cubic structure known as the Verwey transition. Optical studies show that this metal to insulator transition is sharp and occurs around 120 K. [ 24 ] The Verwey transition is dependent on grain size, domain state, pressure, [ 25 ] and ...
At the x = 0 end is magnetite, while the x = 1 composition is ulvöspinel. The titanomagnetites have an inverse spinel crystal structure and at high temperatures are a solid solution series. Crystals formed from titanomagnetites by cation-deficient oxidation are called titanomaghemites, an important example of which is maghemite.
Magnetite-bearing magnetosomes have also been found in eukaryotic magnetotactic algae, with each cell containing several thousand crystals. Overall, magnetosome crystals have high chemical purity, narrow size ranges, species-specific crystal morphologies and exhibit specific arrangements within the
[9] [10] [11] This inhomogeneous crystalline structure gives this variety of magnetite sufficient coercivity to remain magnetized and thus be a permanent magnet. [9] [10] [11] The other question is how lodestones get magnetized. The Earth's magnetic field at 0.5 gauss is too weak to magnetize a lodestone by itself.
Magnetite has an inverse spinel structure with oxygen forming a face-centered cubic crystal system. In magnetite, all tetrahedral sites are occupied by Fe 3+ and octahedral sites are occupied by both Fe 3+ and Fe 2+. Maghemite differs from magnetite in that all or most of the iron is in the trivalent state (Fe 3+
Magnetite (Fe 3 O 4), a mineral of great importance to rock magnetism and paleomagnetism, has an isotropic point at 130 kelvin. [9] Magnetite also has a phase transition at which the crystal symmetry changes from cubic (above) to monoclinic or possibly triclinic below. The temperature at which this occurs, called the Verwey temperature, is 120 ...
The anion is normally oxygen; when other chalcogenides constitute the anion sublattice the structure is referred to as a thiospinel. A and B can also be the same metal with different valences, as is the case with magnetite, Fe 3 O 4 (as Fe 2+ Fe 3+ 2 O 2− 4), which is the most abundant member of the spinel group. [3]
Iron(II,III) oxide, or black iron oxide, is the chemical compound with formula Fe 3 O 4.It occurs in nature as the mineral magnetite.It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (Fe 2 O 3) which also occurs naturally as the mineral hematite.