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Local structure study of the orbital order/disorder transition in LaMnO 3

DOI: 10.1103/PhysRevB.95.174107 DOI Help

Authors: Peter M. M. Thygesen (University of Oxford) , Callum A. Young (University of Oxford) , Edward O. R. Beake (University of Oxford; Queen Mary University of London) , Fabio Denis Romero (University of Oxford) , Leigh D. Connor (Diamond Light Source) , Thomas E. Proffen (Spallation Neutron Source) , Anthony E. Phillips (Queen Mary University of London) , Matthew G. Tucker (Diamond Light Source; Spallation Neutron Source; ISIS Facility) , Michael A. Hayward (University of Oxford) , David A. Keen (ISIS Facility) , Andrew L. Goodwin (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 95

State: Published (Approved)
Published: May 2017
Diamond Proposal Number(s): 7904

Abstract: We use a combination of neutron and x-ray total scattering measurements together with pair distribution function (PDF) analysis to characterize the variation in local structure across the orbital order/disorder transition in LaMnO3. Our experimental data are inconsistent with a conventional order/disorder description of the transition, and reflect instead the existence of a discontinuous change in local structure between ordered and disordered states. Within the orbital ordered regime, the neutron and x-ray PDFs are best described by a local structure model with the same local orbital arrangements as those observed in the average (long-range) crystal structure. We show that a variety of meaningfully different local orbital arrangement models can give fits of comparable quality to the experimental PDFs collected within the disordered regime; nevertheless, our data show a subtle but consistent preference for the anisotropic Potts model proposed previously [M. R. Ahmed and G. A. Gehring, Phys. Rev. B 79, 174106 (2009)]. The key implications of this model are electronic and magnetic isotropy together with the loss of local inversion symmetry at the Mn site. We conclude with a critical assessment of the interpretation of PDF measurements when characterizing local symmetry breaking in functional materials.

Subject Areas: Physics

Instruments: I12-JEEP: Joint Engineering, Environmental and Processing