Investigation of the Low Frequency Polarization Mechanisms in Magnetic Fluids

Abstract

The dielectric behaviour of a magnetic uid with magnetite particles dispersed in kerosene was analyzed. Therefore, the frequency (f ) and temperature (T ) dependences of the complex dielectric permittivity, ε(f, T ), over the ranges 4 kHz to 2 MHz and 25• C to 90• C were measured. Based on the experimental results of ε(f, T ) and using the ClausiusMossotti equation, we have determined the temperature dependence of the real part of the total polarizability α , of a magnetic uid. The computations have taken into account that the magnetic uid consists of three components, namely magnetite particles, surfactant, and carrier liquid. The results show that at a given frequency, α increases with temperature in the low frequency range (4 kHz to 100 kHz) and decreases with temperature above 100 kHz. This behaviour demonstrates that in low frequency range the polarization mechanism related to the deformation of the counter ions atmosphere around each particle is predominant and above 100 kHz the orientation of the dipole moments is the main polarization mechanism of the magnetic uid. These measurements enabled the evaluation of the eective dipole moment of the magnetic uid, in order of 1.21 × 10 −30 C m.