Dresden 2006 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
DF: Dielektrische Festkörper
DF 8: Spectroscopy, Scanning and Diffraction Methods
DF 8.1: Hauptvortrag
Mittwoch, 29. März 2006, 14:30–15:10, M{\"U}L Elch
Phonons in multiferroics: BiFeO3 and related systems — •Jens Kreisel1, Raphaël Haumont1,2, Pierre Bouvier3, and Françoise Hippert1 — 1ENS de Physique de Grenoble (F), CNRS — 2Université d’Orsay (F) — 3ENSEE Grenoble (F), CNRS
On the way towards a fundamental understanding of magnetoelectric multiferroics the experimental observation and understanding of the coupling mechanism between the ferroelectric and magnetic order are of great interest. Very little is currently known about the behavior of phonons in magnetoelectric multiferroics, and this although investigations of phonons have in the past played a crucial role in the understanding of classic ferroelectrics.
Motivated to determine and understand the role of phonons in multiferroics, we will discuss the phonon spectrum measured by Raman spectroscopy of the model system bismuth ferrite BiFeO3 (BFO). Further to the discussion of Raman spectra from BFO powder, single crystalline and thin film samples we will compare our results to those from similar but not multiferroic RFeO3 samples.
Key points that will be addressed are: 1) A paraelectric-to-ferroelectric phase transition which is not soft-mode-driven in BFO, 2) Colossal phonon anomalies for BFO around the Néel temperature for some particular phonons, while this is not observed for non multiferroic EuFeO3. The results are discussed in the context of spin-phonon coupling and interactions between magnetic and ferroelectric order parameters. 3) A significant difference in Raman spectra between bulk and thin film BFO samples illustrating the role of epitaxial strain.