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Determination of the sequence and magnitude of charge order in LuFe2O4 by resonant x-ray scattering

DOI: 10.1103/PhysRevB.90.085130 DOI Help

Authors: Sara Lafuerza Bielsa (ESRF-The European Synchrotron; CSIC-Universidad de Zaragoza) , Gloria Subias (CSIC-Universidad de Zaragoza) , Joaquin Garcia (CSIC-Universidad de Zaragoza) , Javier Blasco (CSIC-Universidad de Zaragoza) , Gareth Nisbet (Diamond Light Source) , Kazimierz Conder (Paul Scherrer Institut) , Ekaterina Pomjakushina (Paul Scherrer Institut)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 90 (8) , PAGES 6077-6086

State: Published (Approved)
Published: August 2014

Abstract: We have investigated the low-temperature phases of LuFe 2 O 4 by resonant x-ray scattering (RXS) at the Fe K edge to determine both the ordering sequence and magnitude of charge segregation. Two successive charge ordering (CO) phases have been detected. Resonant superlattice ( 1 / 3 , 1 / 3 , l / 2 ) reflections appear below the so-called CO phase at T CO ≈ 320 K. Additionally, resonant superlattice ( 1 / 3 , 1 / 3 , l ) reflections are observed below 240 K concurrent with the onset of the magnetic ordering. The σ-σ′ polarization dependence for all the measured superlattice reflections indicates the absence of local anisotropy of the electronic density at the Fe atom. The energy dependence of the resonant intensity for these reflections has been quantitatively analyzed following the monoclinic C 2 / m structure in the CO phase between 320 and 240 K and the triclinic P ¯ 1 structure below 240 K. We find a four-modal charge segregation among the Fe atoms in the C 2 / m phase with formal valences Fe 2.77 + , Fe 2.63 + , Fe 2.36 + , and Fe 2.22 + whereas the simplest charge distribution that explains successfully all the RXS data in the P ¯ 1 phase is the trimodal Fe 2.8 + , Fe 2.5 + , and Fe 2.2 + . Both ordering models imply the lack of charge segregation along the c axis discarding a polar configuration and thus the occurrence of ferroelectricity.

Diamond Keywords: Ferroelectricity

Subject Areas: Physics, Materials

Instruments: I16-Materials and Magnetism

Added On: 04/09/2014 10:55

Discipline Tags:

Quantum Materials Hard condensed matter - electronic properties Physics Materials Science

Technical Tags:

Scattering Resonant Soft X-ray Scattering (RSXS)