Macrodiffusion of colloidal ferroparticles in weak magnetic fields

The effect of a low-strength magnetic field on macroscopic diffusion of fer romagnetic colloidal particles is studied on the basis of thermodynamics. T his effect is caused by two different mechanisms: particle magnetic interac tions and concentration perturbations of the field. The ratio between the c hanges in the diffusion coefficient in fields that are oriented parallel an d perpendicular to the concentration gradient depends only on the concentra tion dependence of the initial susceptibility of the ferrocolloid, and the pattern of the dependence of this ratio on susceptibility is fundamentally different for different known models of magnetization. Therefore, diffusion experiments may be used to select the models of particle interaction in st udies of the thermodynamic properties of colloids in an external field.