The complex magnetic and dielectric properties of bi-dispersed magnetic fluids

Abstract

The bi-dispersed magnetic fluids are prepared by dispersing commercially purchased micron-sized iron (III) oxide particles (Fe2O3) (<5µm) in the laboratory-prepared kerosene-based magnetic nanofluid (Fe3O4 nanoparticles in kerosene). The magnetic and dielectric properties, complex magnetic permeability (μ*), and complex dielectric permittivity (ε*), of the bi-dispersed magnetic fluids, are studied as a function of frequency, concentration of micron-sized particles and time, in the broad frequency range (0.3 MHz to 3 GHz). It is shown that energy absorption occurs due to the phenomena called magnetic relaxation and ferromagnetic resonance. The energy absorption is enhanced in the fluid due to the presence of micron-sized particles. As time progresses, these properties get modified significantly. The magnetic and dielectric properties of bi-dispersed magnetic fluids deteriorate with time. This is attributed to the occurrence of sedimentation with time in the bi-dispersed magnetic fluids. The occurrence of sedimentation is confirmed by a simple inductance-based experimental technique. The magnetic and dielectric properties at high frequencies are sensitive to the occurrence of sedimentation in the fluid.