Abstract
The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO were measured for temperatures K, using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO closely resembles that of similar Fe perovskites, such as LaFeO, despite the cycloid modulation in BiFeO. We do not find any evidence for a spin gap. A strong 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 dependence of Bi-dominated modes across the Néel transition. These results highlight the importance of spin-phonon coupling in this material.
1 More- Received 12 November 2011
DOI:https://doi.org/10.1103/PhysRevB.85.064405
©2012 American Physical Society