Relaxation dynamics of multiferroic rare-earth manganites

In recent years, multiferroic compounds attracted an enormous scientific and technological interest. This rare class of materials combines ferroelectricity with (anti-)ferromagnetism in a single phase. In rare cases both order parameters are strongly coupled, leading to pronounced magnetocapacitive effects. Prominent examples for such systems are rare-earth manganites like, e.g., TbMnO3. In these compounds partial frustration of the Mn-spins leads to spiral magnetic structures, which allow for a finite ferroelectric polarization. Besides the transition to the multiferroic phases, dielectric spectroscopy reveals a relaxation along the c-direction in these materials. We provide the results of a detailed investigation of the relaxation dynamics in several rare-earth manganites (GdMnO3, Eu:YMnO3, TbMnO3, DyMnO3). This dynamics seems to play an important role for the magnetocapacitive properties of these compounds