Nanoporous ferrimagnetic and ferromagnetic membranes are considered for separation of paramagnetic and diamagnetic species. The prepared ferrimagnetic membranes are based on maghemite (γ-Fe₂O₃) and cobalt ferrite (Fe₂CoO₄). Ferromagnetic films of (Fe_0.67Co_0.33)₈₉–B_2.75N_8.25 (FeCo–B–N) are prepared on porous substrates by reactive rf magnetron sputtering. O₂–N₂ adsorption, air separation and ion selectivity experiments are carried out in order to evaluate magnetic interactions in static and dynamic conditions, respectively. A slight effect of an external magnetic field on the selectivity of the membranes is shown. Optimization of the membrane porosity and magnetic properties remains possible (decrease of the pore size to increase the magnetic interactions). It seems, however, difficult to get easily high-performance membranes required for technological applications.