Impact of structurization in colloidal solution of ferromagnetic nanoparticles on demagnetization factor of the sample

In experiment, the effective coefficient of demagnetization the sample of colloidal solution ferromagnetic nanoparticles was measured by method of NMR. This solution was put in two long cylindrical tubes parallel to intensity of external magnetic field and having diameters are 10 times less than the height of the liquid. It is found that the measured coefficient of demagnetization N ≈ 0.09, while in theory N = 0.02. The effect is explained by the presence of conglomerates of nanoparticles.