Temperature-dependent Raman scattering of multiferroicPb(Fe1/2Nb1/2)O3

Abstract

Raman scattering measurements on multiferroicPb(Fe1/2Nb1/2)O3 over a wide temperature range from 10 to 500 K were performed. Very broad andoverlapping peaks (first-order character) and a prominent high-frequency peak at ∼ 1130 cm − 1, which we assign as a two-phonon peak, were observed. These features showed remarkablechanges in their Raman scattering intensity and spectral shape at the characteristic temperatureT* ∼ 330 K, clearly showing a structural lattice change at aroundT*. The temperature dependence of some stretching vibration modes of theBO6 units revealed an anomalous frequency shift belowTN ∼ 143 K. These anomalousdeviations at TN of the phonon frequency are associated with the spin–phonon couplingmechanism. Complementary magnetic data confirmed a weak magneticordering at room temperature and interestingly showed an anomaly at aboutT*. These results suggest an interplay between ferroelectric, structural andmagnetic degrees of freedom in PFN, starting to be significant at aroundT*.