Dielectric spectroscopy of magnetic fluid based on transformer oil

Polarization and relaxation processes in a magnetic fluid can be characterized by the complex permittivity and dissipation factor. The change of these parameters and rearrangement of magnetic nanoparticles in an electric field and magnetic flux density were studied by dielectric spectroscopy. The frequency dependences of dielectric parameters were measured in a wide frequency range from 1 mHz to 10 kHz at a wide range of temperatures from −35 °C to 35 °C at the application of the magnetic flux density and the electric field by a capacitance method. The object of our study was the magnetic fluid based on transformer oil TO 40 A MOL with FeO·Fe2O3 magnetic nanoparticles. The development of the dissipation factor of studied magnetic fluid show one low-frequency relaxation maximum at the eigenfrequency, which was associated with the electric double-layer. The Cole-Cole relaxation model was used for analyzing measured data, and the activation energy from the Arrhenius plot was calculated.