Anharmonic phonons and magnons in BiFeO3

作者：Delaire O^*; Stone M B; Ma J; Huq A; Gout D; Brown C; Wang K F; Ren Z F

来源：Physical Review B, 2012, 85(6): 064405.

DOI：10.1103/PhysRevB.85.064405

The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO3 were measured for temperatures 200 %26lt;= T %26lt;= 750 K, using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO3 closely resembles that of similar Fe perovskites, such as LaFeO3, despite the cycloid modulation in BiFeO3. 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 Neel transition. These results highlight the importance of spin-phonon coupling in this material.

• 出版日期2012-2-13