Magnetically frustrated behavior in multiferroics RMn2O5 (R=Bi, Eu, and Dy): A Raman scattering study

• Published in: Journal of applied physics 2007-05, Vol.101 (9)
• Main Authors: García-Flores, A. F., Granado, E., Martinho, H., Rettori, C., Golovenchits, E. I., Sanina, V. A., Oseroff, S. B., Park, S., Cheong, S.-W.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2712955

A temperature dependent Raman scattering study in multiferroic single crystals RMn2O5 (R=Bi, Eu, and Dy) was performed. The Raman spectra were measured in the range from 150to450cm−1 involving mostly Mn–O–Mn bending vibrations, complementing our previous work in a higher frequency range involving Mn–O stretching modes. A number of studied phonons present anomalous frequency behavior below a characteristic temperature, T*∼60–65K, such as that found for the stretching modes. The sign and magnitude of such anomalous behavior appear to be correlated with the ionic radius of R, being softening for R=Bi and hardening for R=Eu and Dy in the range between TC∕TN and T*. The anomalous phonon behaviors in both bending and stretching modes are consistent with an interpretation in terms of the spin-phonon coupling in a scenario of strong magnetic correlations.