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Maghemite (Fe 2 O 3, γ-Fe 2 O 3) is a member of the family of iron oxides. It has the same formula as hematite , but the same spinel ferrite structure as magnetite ( Fe 3 O 4 ) and is also ferrimagnetic .
Maghemite differs from magnetite in that all or most of the iron is in the trivalent state (Fe 3+) and by the presence of cation vacancies in the octahedral sites. Maghemite has a cubic unit cell in which each cell contains 32 oxygen ions, 21 1 ⁄ 3 Fe 3+ ions and 2 2 ⁄ 3 vacancies. The cations are distributed randomly over the 8 tetrahedral ...
It is metastable and converted from the alpha phase at high temperatures. It occurs naturally as the mineral maghemite. It is ferromagnetic and finds application in recording tapes, [12] although ultrafine particles smaller than 10 nanometers are superparamagnetic. It can be prepared by thermal dehydratation of gamma iron(III) oxide-hydroxide.
Ferrite nanoparticles or iron oxide nanoparticles (iron oxides in crystal structure of maghemite or magnetite) are the most explored magnetic nanoparticles up to date.Once the ferrite particles become smaller than 128 nm [22] they become superparamagnetic which prevents self agglomeration since they exhibit their magnetic behavior only when an external magnetic field is applied.
Maghemite is a polymorph of hematite (γ-Fe 2 O 3) with the same chemical formula, but with a spinel structure like magnetite. Large deposits of hematite are found in banded iron formations. Gray hematite is typically found in places that have still, standing water, or mineral hot springs, such as those in Yellowstone National Park in North ...
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.
Gossans of nickel mineralisation, especially massive sulfides, are dominated in the arid Yilgarn Craton by boxworks of goethite, hematite, maghemite and ocher clays. Non-sulfide nickel minerals are typically soluble, and preserved rarely at surface as carbonates, although often can be preserved as nickel arsenates ( nickeline ) within gossans.
Magnetite is one of the very few minerals that is ferrimagnetic; it is attracted by a magnet as shown here Unit cell of magnetite. The gray spheres are oxygen, green are divalent iron, blue are trivalent iron.