Magnetic transient birefringence of ferrofluids : particle size determination

Abstract

Relaxation time measurements of magnetically induced birefringence of ferrofluid solutions are performed with samples of various polydispersities. d H, the hydrodynamic diameter of particles deduced from experiments, is compared to a numerical computation with a log-normal distribution. Dynamic magnetic birefringence appears to be a good test of the tail of the sample size distribution. For a narrow distribution (σ ≃ 0.25), the experiment is in good agreement with the model: dH is two times larger than the most probable diameter and corresponds to the largest particles in the sample