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We present a dielectric spectroscopy study of the polar dynamics linked to the orbitally driven ferroelectric transition in the Skyrmion host GaV4S8. By combining THz and MHz-GHz spectroscopy techniques, we succeed in detecting the relaxational dynamics arising from coupled orbital and polar fluctuations in this material and trace its temperature dependence in the paraelectric as well as in the ferroelectric phase. The relaxation time significantly increases when approaching the critical temperature from both sides of the transition. It is natural to assume that these polar fluctuations map the orbital dynamics at the Jahn-Teller transition. Because of the first-order character of the orbital-ordering transition, the relaxation time shows an enormous jump of about 5 orders of magnitude at the polar and structural phase transition. [ABSTRACT FROM AUTHOR]

We deduce the intrinsic conductivity properties of the ferroelectric domain walls around the topologically protected domain vortex cores in multiferroic YMnO3. This is achieved by performing a careful equivalent-circuit analysis of dielectric spectra measured in single-crystalline samples with different vortex densities. The conductivity contrast between the bulk domains and the less conducting domain boundaries is revealed to reach up to a factor of 500 at room temperature, depending on the sample preparation. Tunneling of localized defect charge carriers is the dominant charge-transport process in the domain walls that are depleted of mobile charge carriers. This work demonstrates that, via equivalent-circuit analysis, dielectric spectroscopy can provide valuable information on the intrinsic charge-transport properties of ferroelectric domain walls, which is of high relevance for the design of new domain-wall-based microelectronic devices. [ABSTRACT FROM AUTHOR]