Raman Spectra of Multiferroics TbMnO3
Raman Spectra of Multiferroics TbMnO3
Author : ISMUDIATI PURI H. Published on : MRS-ID Meeting 2014 (ASTON HOTEL DENPASAR, BALI, INDONESIA)
Abstract
The dream to have multifunctional materials has triggered an intense study of multiferroicity, i.e. of materials in which magnetic and electric polarizations are simultaneously present and strongly coupled. Here we study TbMnO3, a perovskite manganite exhibiting multiferroicity. It has an incommensurate antiferromagnetic ordering transition at 41 K and a transition into a multiferroic spin spiral state at 26 K. In these materials, fundamental excitations such as phonons, magnons, and electro-magnons can be studied to characterize the various phase transitions, as well as to unravel the interactions between the various degrees of freedom. In this study, Raman spectroscopy has been used to elucidate the nature of the excitations. We show that the optical phonons in TbMnO3 resemble the phonon characteristics typical for perovskite manganites, corresponding to MnO6 octahedral vibrations. The appearance of a new low energy modes at 32 cm-1, 40 cm-1, and 63 cm-1 observed below 41 K signifies the antiferromagentic ordering in TbMnO3. The 32 cm- 1 and 63 cm-1 are interpreted as spin ordering activated phonon while the 40 cm-1 is interpreted as spin ordering induced splitting of Tb quasi doublet cystal field level.
