Low frequency excitations in multiferroic MnWO4

Dynamic anomalies have been found in the magnetically ordered phases of multiferroic MnWO4 using polarized Raman scattering. Strong phonon damping is observed for several B-g modes within the ferroelectric phase and has been attributed to spin-phonon interactions. Moreover, a new low frequency excitation was detected near 33 cm(-1) that grows in intensity on cooling into the antiferromagnetic phases. It is argued that this signal is most probably due to a two-magnon process.