Maghemite


Maghemite (γFe2O3) is the fully oxidized equivalent of magnetite. Maghemite forms through the low temperature oxidation of magnetite, which typically occurs during weathering. A solid solution series of titanomaghemites is formed through oxidation of titanomagnetites. Maghemite inverts to hematite during heating. The temperature of inversion has been measured from 250 to 750 °C[1] . Maghemite can also invert during heating to form magnetite; the product of inversion depends on the initial composition of the maghemite. The inversion of maghemite makes determination of its Curie temperature difficult, and reported values vary from 470 to 695 °C, with the best estimate thought to be ~645 °C¹ . The variability of Tc in naturally occurring maghemite can be attributed to strain, structural imperfections, and impurities.

Physical Properties




Physical
Parameter
Description
/Value¹
Units
Chemical
formula
γFe2O3
N/A
Density

kg.m-3
Unit cell
8.337 (a0)
24.99 (c0)
Å
Colour

N/A
Crystal habit

N/A
Moh's hardness

N/A



Magnetic Properties



Physical
Parameter
Description
/Value¹
Units
Magnetic
ordering
Ferrimagnetic
N/A
Ms
380
kA.m-1
Tc
590–675
(°C)
K
-4.65x103
J.m-3




Common Occurrences




References


  1. ^ Dunlop, D. J., and Ö. Ö zdemir (1997), Rock Magnetism: Fundamentals and Frontiers, Cambridge Stud. Magn., vol. 3, Cambridge Univ. Press, New York.





Further Reading

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See Also


List of other relevant MagWiki pages.