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In this letter, we investigated the temperature-dependent Raman spectra of CaMn7O12 helimagnet from room temperature down to 10 K. The temperature dependence of the Raman mode parameters shows remarkable anomalies for both antiferromagnetic and incommensurate transitions that this compound undergoes at low temperatures. The anomalies observed at the magnetic ordering transition indicate a spin-phonon coupling at higher-temperature magnetic transition in this material, while a magnetostriction effect at the lower-temperature magnetic transition.

We have synthesized two divanadates M2V2O7 (M2+ = Co2+ and Cu2+), that are known to show different and complex magnetic arrangements at low temperatures and have studied their dielectric behavior. We have observed a change in the slope of the dielectric constant at the magnetic transition temperature, result which confirms the existence of magnetodielectric coupling in these two divanadates. The origin of the magnetodielectric coupling seems to be different in the Cu- and Co-compounds, although in both cases it is related to their frustrated magnetic arrangement. In Cu2V2O7, the dielectric anomaly arises from a spin canting due to the antisymmetric exchange which is allowed by structural symmetry. In the Co-divanadate, the structural symmetry does not allow antisymmetric exchange but the compound shows correlation between the behavior of the dielectric constant and inverse magnetization, which points to a dependence of its electrical polarization with the pair correlation function of neighboring magnetic spins.

We present a detailed investigation on the magnetodielectric properties of Fe2OBO3, where we have found a magnetodielectric effect around 150% at room temperature and ν=2 kHz, that cannot solely arise from magnetoresistive extrinsic contributions. In addition, we find a crossover of the magnetodielectric response around TN, that we attribute to changes in the electronic microstructure of this compound that take place at that temperature. For T

We report the optimization of the dielectric properties of La2/3Ca1/3MnO3. This is achieved by synthesizing this material with small particle size, strategy that reduces the conductivity of the sample and its dielectric losses, while retaining a reasonably high dielectric permittivity and a good magnetocapacitive response. In order to further improve the properties of these nanoparticles, we have also prepared core-shell composites La2/3Ca1/3MnO3@SiO2 but in this case the magnetocapacitive effect is strongly reduced.