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

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 2x10(16) to 8x10(16) particle/cm(3) 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. (C) 2001 American Institute of Physics.