TRANSVERSE SUSCEPTIBILITY OF MAGNETIC INKS

The transverse susceptibility, chi(t), of a suspension of single-domai n ferromagnetic particles in a viscous fluid is calculated. The yield stress is introduced to describe the structure formation. Magnetic int eractions are taken into account through the mean-field model. Calcula tions are compared to experiments in which a de field, H, is slowly in creased. The experiments were performed on a model iron oxide dispersi on. The function chi(t)(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-fie ld interaction parameter in our model. (C) 1997 American Institute of Physics.