Investigation on the nature of the Verwey Transition in Cu-doped Fe3O4
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Date
2018-01-31
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Australian Institute of Physics
Abstract
Magnetite (Fe3O4), the oldest known magnet, is still a hotly debated material in scientific research, due to its complex magnetic, electronic and transport properties. One of the most interesting physical phenomena associated with Fe3O4 is the occurrence of a metal-insulator transition at ~120 K (TV), the so-called Verwey transition, which was associated with charge ordering below TV, accompanied by a structural transition from the cubic phase to the monoclinic phase. However, due to the twinning of crystal domains, the detailed crystallographic structure is not fully solved yet and different charge ordered and bond-dimerized ground states have been proposed. In order to overcome this problem, we have investigated Cu-doped Fe3O4 to approach the problem through the determination of the phase diagram of Fe1-xCuxFe2O4. Using neutron diffraction and high resolution X-ray synchrotron diffraction we have investigated both the crystallographic and magnetic structure of Cu-doped Fe3O4 in order to elucidate the effect of doping on the Verwey transition. Data obtained from both complementary diffraction techniques indicate that the Verwey transition temperature and the magnetic structure, in particular the magnetic moment, remain unchanged up to high doping levels of 85% Cu-substitution. This is a surprising result at first glance and required a systematic investigation. The analysis of our high resolution X-ray synchrotron diffraction data allowed us to extract detailed information on the precise doping mechanism, including the distribution of Cu-ions between tetrahedral and octahedral sites in the spinel structure. The diffraction data therefore provide valuable information on the detailed mechanism behind the Verwey transition.
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Keywords
Diffraction, Iron ores, Oxide minerals, Physical properties, Scattering, Thermodynamic properties, Crystal doping, Crystal structure, Phase transformations
Citation
Kareri, Y., Chang, F., Hester, J. & Ulrich, C. (2018). Investigation on the nature of the Verwey Transition in Cu-doped Fe3O4. Poster presented to the 42nd Annual Condensed Matter and Materials Meeting, Charles Sturt University, Wagga Wagga, NSW, 30th January – 2nd February, 2018. (pp. 79). Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2018/Wagga_2018_Conference_Handbook.pdf