Structural and Magnetic Phase Transitions in Minerals: In Situ Studies by Neutron Scattering

Redfern, S. A. T. and Harrison, R. J. (2009) Structural and Magnetic Phase Transitions in Minerals: In Situ Studies by Neutron Scattering. In: Neutron Applications in Earth, Energy and Environmental Sciences. Springer US, pp. 107-143. ISBN 978-0-387-09415-1 (Print) 978-0-387-09416-8 (Online)

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Official URL: doi:10.1007/978-0-387-09416-8_4

Abstract

The application of neutron scattering to the study of structural and magnetic phase transitions in minerals is discussed. The advantages of neutrons for structural characterization of phase transitions are enumerated and compared with the data that might be obtained from X-ray methods. Elements that are difficult to distinguish by X-ray diffraction can show huge contrasts in neutron diffraction experiments; this contrast has been exploited in studies of site occupancies and intra-mineral partitioning of elements difficult to distinguish by other methods, such as Mg–Al and Fe–Mn pairs. Selected examples of the use of these methods in recent studies are outlined. These include the study of cation order–disorder phase transitions in minerals, ranging in complexity from rather simple silicate structures such as olivine and spinel (where ordering may occur between two sites)to more complex double-chain silicates (where partitioning studies by neutron diffraction have identified the trends over as many as four different crystallographic sites). The ability to build complex sample environments around the minerals under study has been beneficial in cases where extreme high temperatures (as great as 2000 K) are of interest, or where buffering of oxidation states is required. The magnetic moment of the neutron provides a unique tool for the study of the magnetic structures of oxide minerals, and the identification of magnetic ordering schemes in minerals such as magnetite were some of the first examples of the application of this method to magnetic minerals. The principles of magnetic scattering of neutrons are briefly outlined; and applications of magnetic studies by powder diffraction using both unpolarized and polarized neutrons are discussed, including recent studies of nanoscale hematite exsolution in ilmenite by polarized neutron scattering. Finally, the extension of the entire family of such studies in mineralogy to conditions pertinent to deep planetary interiors is considered as an example of the sophisticated high-pressure and high-temperature sample environment apparatus that has been developed for mineralogical studies.

Item Type: Book Section
Uncontrolled Keywords: 08AREP; IA57;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Volume: Part I
Page Range: pp. 107-143
Depositing User: Sarah Humbert
Date Deposited: 20 May 2009 13:00
Last Modified: 23 Jul 2013 09:54
URI: http://eprints.esc.cam.ac.uk/id/eprint/995

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