Anharmonic phonons and magnons in BiFeO 3

O. Delaire, M. B. Stone, J. Ma, A. Huq, D. Gout, C. Brown, K. F. Wang, Z. F. Ren

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Abstract

The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO 3 were measured for temperatures 200≤T≤750K, using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO 3 closely resembles that of similar Fe perovskites, such as LaFeO 3, despite the cycloid modulation in BiFeO 3. We do not find any evidence for a spin gap. A strong T dependence of the phonon DOS was found, with a marked broadening of the whole spectrum, providing evidence of strong anharmonicity. This anharmonicity is corroborated by large-amplitude motions of Bi and O ions observed with neutron diffraction. A clear anomaly is seen in the T dependence of Bi-dominated modes across the Néel transition. These results highlight the importance of spin-phonon coupling in this material.

Original languageEnglish
Article number064405
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume85
Issue number6
DOIs
StatePublished - Feb 13 2012

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