Transverse susceptibility of magnetic inks

Abstract

The transverse susceptibility, χt, of a suspension of single-domain ferromagnetic particles in a viscous fluid is calculated. The yield stress is introduced to describe the structure formation. Magnetic interactions are taken into account through the mean-field model. Calculations are compared to experiments in which a dc field, H, is slowly increased. The experiments were performed on a model iron oxide dispersion. The function χt(H) goes through a maximum which decreases and shifts to a higher field when the pigment concentration is increased. This is attributed to an increase of the yield stress and the mean-field interaction parameter in our model.

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

“…The complex susceptibility of magnetic colloids () is measured in the frequency range 10 Hz-10 kHz on a previously described instrument (6). Generally, the magnetic paint is subjected to a homogeneous AC magnetic field.…”

“…cannot be used for studying these magnetic colloids. Only a few experimental techniques such as rheology (4), electroacoustics (5), and transverse susceptibility measurements (6) provide an adequate view inside the magnetic paints, but none of these techniques alone provides a complete picture. The present work is the first attempt to study the properties of concentrated magnetic colloids by measuring the frequency dependence of the AC magnetic susceptibility.…”