1205.3551 (Venkata Srinu Bhadram et al.)

Correlation between Spin-Phonon Coupling and Ferroelectricity in
RCrO$_3$ (R=Y, Gd, Sm): A Raman Study    [PDF]

Venkata Srinu Bhadram, B. Rajeswaran, A. Sundaresan, Chandrabhas Narayana

We have carried out a temperature-dependent Raman study of orthochromites, RCrO$_3$ (R = Gd, Sm and Y) to probe the role of magnetic R-ions in inducing ferroelectricity at the N\'eel temperature (TN) of chromium. Our results show that the phonon behavior at TN in compounds with magnetic R-ion (Gd and Sm) is remarkably different from that of non-magnetic R-ion (Y). A strong spin-phonon coupling is evidenced from the anomalies in all the observed phonon frequencies and their line-widths at TN for the compounds with magnetic R-ion. In the case of nonmagnetic R-ion, the anomalous behavior observed in certain phonon frequencies is due to mangetostriction. In addition, the anomalies in the low frequency modes related to R-atom motion in SmCrO$_3$ and GdCrO$_3$ accounts for the displacement of the magnetic R$^{3+}$ ion resulting in ferroelectric polarization.

View original: http://arxiv.org/abs/1205.3551