THE TIME-DEPENDENCE OF PARTICLE AGGREGATION IN MAGNETIC FLUID LAYERS

The time evolution of the field-induced formation of magnetic particles into macro-clusters, including the areal density of the macro-clusters as a function of the time in a magnetic fluid thin layer ( < 20 mum), is investigated using an optical microscope. A magnetic field increasing linearly with time is applied perpendicular to the layer plane. The results show that for the given magnetic field the corresponding macro-cluster areal density depends upon the initial ordering of macro-clusters and upon the details of the magnetic field application sequence. Some parameters describing the microscopic observations such as the number, size and mutual ordering of macro-clusters are dependent on the magnetic field history.