Raman scattering studies on multiferroicYMnO3

Abstract

YMnO3 is amultiferroic material in which ferroelectric and antiferromagnetic ordering can coexist. We have studieda YMnO3 bulk crystal in detail by Raman scattering in a wide temperature range of 15–1200 K, withcomparison to a previous experiment at room temperature and a theoretical prediction forRaman-active phonon modes. In the low-temperature ferroelectric phase, the observedphonon spectra showed anomalous temperature variation at the Néel temperature,TN∼80 K, suggesting a coupling between the spin and phonon systems belowTN. Furthermore, spectra for the high-temperature paraelectric phase, reportedhere for the first time, showed a sudden change at the Curie temperatureTC>900 K, suggesting an abrupt structural phase change from the ferroelectric to the paraelectricphase.