New technique for measuring the complex susceptibility of ferrofluids

AC Susceptibility Measurements in the Investigation of Aggregation in Magnetic Fluids

“…The frequency-dependent complex susceptibility of two ferrofluid samples, namely fluids 1 and 2, was measured by means of the toroidal technique [7] over the frequency range 10 Hz to 1 MHz. The two fluids consisted of suspensions of magnetite in water with corresponding saturation magnetisations of 107 Gs and 90 Gs and mean magnetic particle radii, as determined by electron micrography, of 7 nm and 6 nm respectively.…”

Determination of the Size Distribution of Magnetite Nanoparticles from Magnetic Measurements

“…Complex ac susceptibilities were measured at room temperature in the frequency range of 40 Hz -110 MHz by means of the slittoroid method [16] using an HP4294A impedance analyzer. We used a high permeability toroid with a 0.35 mm slit wound with 15 turns of litz wire.…”

Characterisation of magnetic fluids

“…Whilst this technique is suitable for single frequency measurement [11] it has many limiting factor for use over a broad range of frequencies; in such situations the toroidal technique [12] is far superior.…”

“…1(a), obtained by means of the toroidal technique [12], for a suspension of magnetite in water (sample 1); the corresponding mean particle radius as determined by electron microscopy was 5 nm. It is apparent that the plots have a Debye-type profile with a maximum in χ (ω) occurring at 1.25 kHz; from Eq.…”