Iron borate multiferroic a new way to observe electromagnon?

In the last years, multiferroics have attracted much attention worldwide because of their large magnetoelectric effects. We used infrared scattering to probe the dynamical coupling between spin and lattice degrees of freedom in rare earth iron borates. These materials have interesting magnetic properties due to the subtle interactions between the rare earth and the iron moments. Among these materials, NdFe3(BO3)4 becomes multiferroics under magnetic field. At low temperature, a new mode appears at low frequency in the (ab) plane. This mode can be the signature of change in the lattice around the magnetic transition but no structural phase transitions are expected in this compound. This new peak has most probably a magnetic origin, electromagnon? Moreover, along the c direction the lowest phonon mode has its frequency decreasing with temperature and the total dielectric function for the c axis comes from this phonon. This is the typical behavior of a soft phonon mode in a ferroelectric compound. This material is a good candidate to observe the electromagnon.