INFLUENCE OF PARTICLE-SIZE DISTRIBUTION ON THE INITIAL SUSCEPTIBILITYOF MAGNETIC FLUIDS IN THE BROWN RELAXATION RANGE

We present experimental results on magnetic liquids characterised by a size distribution of particles. The initial complex susceptibility ha s been studied in the Brown relaxation range using a polarimetric meth od. The position and the shape of the relaxation peak allow to determi ne apparent values of hydrodynamic mean diameter and its standard devi ation. Theoretical calculations were made from the Debye model includi ng the size distribution of particles and the experimental study shows its influence and the necessity to take it into account for a better results exploitation. In these conditions, the Debye model used gives excellent results in accordance with the experimental points. (C) 1998 Elsevier Science B.V. All rights reserved.