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Phys. Rev. Lett. 103, 077602 (2009) [4 pages]

Direct Observation of Charge Order and an Orbital Glass State in Multiferroic LuFe2O4

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A. M. Mulders1,2, S. M. Lawrence1, U. Staub3, M. Garcia-Fernandez3, V. Scagnoli4, C. Mazzoli4, E. Pomjakushina5,6, K. Conder5, and Y. Wang7
1Department of Imaging and Applied Physics, Curtin University of Technology, Perth, WA 6845, Australia
2The Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia
3Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
4European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex 9, France
5Laboratory for Developments and Methods, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
6Laboratory for Neutron Scattering, ETHZ & PSI, 5232 Villigen, Switzerland
7Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China

Received 15 December 2008; published 12 August 2009

Geometrical frustration of the Fe ions in LuFe2O4 leads to intricate charge and magnetic order and a strong magnetoelectric coupling. Using resonant x-ray diffraction at the Fe K edge, the anomalous scattering factors of both Fe sites are deduced from the (h/3   k/3   l/2) reflections. The chemical shift between the two types of Fe ions equals 4.0(1) eV corresponding to full charge separation into Fe2+ and Fe3+. The polarization and azimuthal angle dependence of the superlattice reflections demonstrate the absence of differences in anisotropic scattering revealing random orientations of the Fe2+ orbitals characteristic of an orbital glass state.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.103.077602
DOI:
10.1103/PhysRevLett.103.077602
PACS:
77.80.−e, 61.05.C−, 75.80.+q
 
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