Dielectric anisotropy (1 MHz - 10 MHz) of a magnetic fluid: Cobalt ferrite in dibutyl phthalata

The authors present a dielectric study of ferrofluid, magnetic particles of Fe₂CoO₄ dispersed in dibutyl phthalata, at different volume concentrations in a large temperature range (from 40°C down to -100°C) between 1 MHz and 10 MHz, with and without a continuous axial or radial magnetic field. The analysis of static permittivity shows a small magnetodielectric anisotropy, even at low temperature, and the possible existence and growth of aggregates at higher concentrations. It is shown that, in the given experimental conditions, and under a continuous longitudinal or transverse magnetic field, this ionic colloidal suspension does not remain well-dispersed above a limit volume concentration (x ≈ 0.05) when temperature is decreasing