SPATIAL-DISTRIBUTION AND FRACTAL PROPERTIES OF AGGREGATING MAGNETIC AND NONMAGNETIC PARTICLES

We study the spatial distribution in aggregating systems of mixtures o f magnetic and nonmagnetic particles using Monte-Carlo simulations tog ether with scaling arguments. In particular, we show that (a) as the s ystem size grows, the fractal dimension of the composite system is dom inated by the smaller fractal dimension, (b) the system is realized as a backbone consisting of magnetic particles (lower fractal dimension) with denser regions of nonmagnetic particles attached to it at random positions. Using simple connectivity features observed in pure magnet ic and non-magnetic clusters and self-similarity arguments we predict via Real-Space-Renormalization, fractal exponents D-m = 1.25 +/- 0.05 for the magnetic clusters and D-nm = 1.4 +/- 0.1 for the non-magnetic clusters.