This paper presents the results of a neutron depolarisation study of the magnetic correlations relations in a particulate dispersion during milling. It appears that clusters or aggregates of particles break up in the first 90 min of the milling process, and in the final stages of milling, when dispersion is diluted, the dispersion does not flocculate. Moreover, the magnetic correlation length within the dispersion remains stable over a period of two weeks after preparation. The results of a numerical approach to predict the microstructure of a non-magnetised dispersion agree well with the experimental results.