TY  - JOUR
JF  - Physical Review B
A1  - Gaw, SM
A1  - Lewtas, HJ
A1  - McMorrow, DF
A1  - Kulda, J
A1  - Ewings, RA
A1  - Perring, TG
A1  - McKinnon, RA
A1  - Balakrishnan, G
A1  - Prabhakaran, D
A1  - Boothroyd, AT
N2  - 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.
ID  - discovery1434306
UR  - http://dx.doi.org/10.1103/PhysRevB.91.035103
SN  - 1098-0121
IS  - 3
N1  - ©2015 American Physical Society
TI  - Magnetic excitation spectrum of LuFe2O4 measured with inelastic neutron scattering
AV  - public
VL  - 91
Y1  - 2015/01/05/
ER  -