Magnetic and optical studies of magnetic colloidal particles in water and oleic acid.

The macro-size magnetic colloidal particles in both distilled water and oleic acid were prepared by using Fe[sub 3]O[sub 4] ferrofluids (SMG018), the sodium dodecyl sulfate (SDS), and distilled water or oleic acid. The optical transmission of these ferrofluid emulsions has been investigated as functions of concentration of SDS between 0.64 and 3.73 wt %, incident optical wavelengths between 450 and 750 nm, and applied magnetic fields up to 141 Oe. The optical transmission shows maximum with concentration of SDS near 3.13 and 1.90 wt % for samples in distilled water and oleic acid, respectively. In general, under an applied magnetic field, the size of the magnetic colloidal particles for samples in oleic acid is smaller than that of samples in distilled water; however, the concentration of the magnetic colloidal particles is the opposite. This can be explained due to the different aggregation ability of the magnetic colloidal particles in both distilled water and oleic acid. The optical transmission of the samples is observed to be reversed proportional to the area covered by the magnetic colloidal particles. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]