Raman spectroscopy is a very valuable and fast-performance tool to gain insight first into the different iron oxide phases present in nanoparticles, to correlate then the magnetic properties with potential bio-related applications.

The origin of dielectric anomalies and magnetodielectric response of La(2)MnCoO(6) has been investigated by means of ultra-high resolution synchrotron x-ray powder diffraction, neutron powder diffraction, resistivity, magnetization and dielectric measurements. The study has been performed on two different bulk samples presenting different degrees of Mn/Co order: 95 and 74%. Beside the well-known influence on magnetic properties, our results show that the main effect of disorder lies on the electrical resistivity. Bond distances clearly show Mn(4+)/Co(2+) valence states in the well-ordered sample, while for the disordered one this picture still holds. AC resistivity data show dielectric anomalies and a small magnetodielectric effect, but impedance complex plane analyses prove that these phenomena appear at the frequency-temperature region where extrinsic effects dominate the dielectric response.

We report the dielectric response of ${\mathrm{La}}_{1.5}{\mathrm{Sr}}_{0.5}\mathrm{Ni}{\mathrm{O}}_4$ , a system that experiences charge ordering above room temperature $(T_{\mathrm{CO}}=480\mathrm{K})$ and a rearrangement of its charge-order pattern in the temperature region $160–200\mathrm{K}$ . A careful analysis of the role of the electrical contacts used, sample thickness, and grain size on the experimental data allows us to determine that this material exhibits a high intrinsic dielectric constant. In addition, the temperature dependence of the dielectric constant, that shows a maximum in the region of the rearrangement of the charge-order pattern, points to a link between the two phenomena.