The influence of aggregates and relative permeability on the magnetic birefringence in ionic magnetic fluids

Abstract

The static magnetic birefringence (SMB) of nickel-ferrite ionic magnetic fluid was investigated within the oscillating dipole-interaction anisotropy concept proposed by Xu and Ridler [J. Appl. Phys. 82, 326 (1997)]. The model was extended to include the magnetic texture of particle agglomerates and the field dependence of the magnetic permeability. The SMB data of samples subjected or not to a magnetic aging process and presenting particle concentration in the range of 2 × 1016 to 8 × 1016 particle/cm3 were successfully described. The particle size distribution obtained from the fit of the SMB data was discussed in comparison with the data obtained from transmission electron microscopy. © 2001 American Institute of Physics.