The effect of magnetic aging on the static magnetic birefringence (SMB) dat
a of a nickel ferrite-based ionic magnetic fluid was investigated. The trad
itional SMB model was improved to account for both the formation of agglome
rates and the field dependence of the relative permeability associated to m
onomers and chain-like structures. Improvement of the SMB model allows dete
rmination of the sample polydispersity profile in excellent agreement with
the transmission electron microscopy data. (C) 2001 Elsevier Science B.V. A
ll rights reserved.