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Magnetic excitation spectrum of LuFe2O4 measured with inelastic neutron scattering

Gaw, SM; Lewtas, HJ; McMorrow, DF; Kulda, J; Ewings, RA; Perring, TG; McKinnon, RA; ... Boothroyd, AT; + view all (2015) Magnetic excitation spectrum of LuFe2O4 measured with inelastic neutron scattering. Physical Review B , 91 (3) , Article 035103. 10.1103/PhysRevB.91.035103. Green open access

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Abstract

We report neutron inelastic-scattering measurements and analysis of the spectrum of magnons propagating within the Fe2O4 bilayers of LuFe2O4. The observed spectrum is consistent with six magnetic modes and a single prominent gap, which is compatible with a single bilayer magnetic unit cell containing six spins. We model the magnon dispersion by linear spin-wave theory and find very good agreement with the domain-averaged spectrum of a spin-charge bilayer superstructure comprising one Fe3+-rich monolayer and one Fe2+-rich monolayer. These findings indicate the existence of polar bilayers in LuFe2O4. We also discuss a model of charge-segregated nonpolar bilayer order which we argue is not consistent with our data but which we cannot exclude definitively. Weak scattering observed below the magnon gap suggests that a fraction of the bilayers contain other combinations of charged monolayers not included in the model. Refined values for the dominant exchange interactions are reported.

Type: Article
Title: Magnetic excitation spectrum of LuFe2O4 measured with inelastic neutron scattering
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevB.91.035103
Publisher version: http://dx.doi.org/10.1103/PhysRevB.91.035103
Language: English
Additional information: ©2015 American Physical Society
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: https://discovery.ucl.ac.uk/id/eprint/1434306
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