Characterization of Concentrated Magnetic Colloids by Measurements of Frequency Dependence of AC Magnetic Susceptibility

Peikov, Viktor; Lane, Alan M.

doi:10.1006/jcis.1998.5724

Cited by 2 publications

(1 citation statement)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Examples of large magnetic colloidal particles are composite magnetic microspheres, [8][9][10] magnetic paints, 11 elongated iron ͑hydr͒oxide particles of hematite 12 or goethite, 13 and aggregates in destabilized ferrofluids. [14][15][16][17][18][19] For composite microspheres, measuring the complex magnetic susceptibility spectrum is a uniquely reliable way to determine the permanent magnetic dipole moment, since the frequency dependence indicates whether field-induced sample magnetization requires rotational motion of the microparticles.…”

Section: Introductionmentioning

confidence: 99%

Complex magnetic susceptibility setup for spectroscopy in the extremely low-frequency range

Kuipers

Bakelaar

Klokkenburg

et al. 2008

Review of Scientific Instruments

View full text Add to dashboard Cite

A sensitive balanced differential transformer was built to measure complex initial parallel magnetic susceptibility spectra in the 0.01-1000 Hz range. The alternating magnetic field can be chosen sufficiently weak that the magnetic structure of the samples is only slightly perturbed and the low frequencies make it possible to study the rotational dynamics of large magnetic colloidal particles or aggregates dispersed in a liquid. The distinguishing features of the setup are the novel multilayered cylindrical coils with a large sample volume and a large number of secondary turns ͑55 000͒ to measure induced voltages with a good signal-to-noise ratio, the use of a dual channel function generator to provide an ac current to the primary coils and an amplitude-and phase-adjusted compensation voltage to the dual phase differential lock-in amplifier, and the measurement of several vector quantities at each frequency. We present the electrical impedance characteristics of the coils, and we demonstrate the performance of the setup by measurement on magnetic colloidal dispersions covering a wide range of characteristic relaxation frequencies and magnetic susceptibilities, from Ϸ −10 −5 for pure water to Ͼ 1 for concentrated ferrofluids.

show abstract