Charge ordering in CaCuxMn7−xO12 (x = 0.0 and 0.1) compounds

The crystal structure of CaMn7O12 and CaCu0.1Mn6.9O12 has been studied by synchrotron radiation (SR) based powder x-ray diffraction and neutron powder diffraction in the temperature range from 10 K up to 290 K. The lattice parameter a exhibits a minimum at 45 K in CaMn7O12. The c lattice parameter i...

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Bibliographic Details
Published in:Journal of physics. Condensed matter 2008-03, Vol.20 (10), p.104239-104239 (7)
Main Authors: Sławiński, W, Przeniosło, R, Sosnowska, I, Bieringer, M, Margiolaki, I, Fitch, A N, Suard, E
Format: Article
Language:English
Subjects:
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
Inorganic compounds
Physics
Structure of solids and liquids
crystallography
Structure of specific crystalline solids
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Summary:The crystal structure of CaMn7O12 and CaCu0.1Mn6.9O12 has been studied by synchrotron radiation (SR) based powder x-ray diffraction and neutron powder diffraction in the temperature range from 10 K up to 290 K. The lattice parameter a exhibits a minimum at 45 K in CaMn7O12. The c lattice parameter in CaMn7O12 and CaCu0.1Mn6.9O12 has a maximum at the same temperature. Additional Bragg peaks have been found in the SR diffraction patterns in CaMn7O12 and CaCu0.1Mn6.9O12 below 250 K and 220 K, respectively. All diffraction peaks have been indexed as (h,k,l +/- kappa), where kappa was equal to 0.079(15) for CaMn7O12 and 0.093(15) for CaCu0.1Mn6.9O12. The incommensurate low-temperature diffraction peaks are not observed in neutron diffraction patterns. This leads to the conclusion that the phase transition to the incommensurate structure is due to charge ordering rather than atomic position modulation. The charge ordering temperature coincides with dielectric constant changes of four orders of magnitude for CaMn7O12.
ISSN:0953-8984
1361-648X
DOI:10.1088/0953-8984/20/10/104239