Anharmonic Phonons and Magnons in BiFeO3

Abstract

The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO${}_3$ were measured for temperatures $200\le T\le 750$K, 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. These results highlight the importance of spin-phonon coupling in this material.

References in corpus (2)

• Room temperature coexistence of large electric polarization and magnetic order in BiFeO3 single crystals
• Determination of the exchange anisotropy in perovskite antiferromagnets using powder inelastic neutron scattering

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