Optical spectroscopic study on magnetoelectric MnWO$_{4}$

We report optical spectroscopic investigation on a multiferroic oxide compound, MnWO$_{4}$. This compound is known to exhibit ferroelectricity induced by the incommensurate spiral magnetic ordering in a temperature range of 7.6 K and 12.7 K [1]. We grew single crystals of MnWO$_{4}$ by using the floating zone method. To examine the optical anisotropy originating from the monoclinic crystal structure, we measured reflectivity spectra of MnWO$_{4}$ with light polarizations along three crystallographic axes, and calculated the optical conductivity spectra through the Kramers-Kronig transformation for each axis. We discuss the anisotropic phonon structures and electronic structures with temperature and magnetic field dependence in relation to its multiferroic properties. \newline [1] K. Taniguchi \textit{et al}., Phys. Rev. Lett. \textbf{97}, 097203 (2006).