Ferrofluids are liquids having magnetic nanoparticles dispersed in a solvent and covered with surfactants to prevent them from agglomeration. The particles can form smectic like ordering in the presence of magnetic field. We are interested in the interaction of magnetic particles with a magnetized solid wall (TbCo). Particles are held as magnetic dipoles aided by the perpendicular anisotropy of amorphous TbCo layer and are attracted by its gradient field. Thus, mono- to multilayers are likely to form by self-assembly even in remanence magnetization state of TbCo layer. Our interest is to study this self-assembly process with respect to different parameters, like ferrofluid concentration, film thickness. The self-assembly process can be rather slow. Neutron reflectivity and grazing incidence scattering will allow us to study the kinetics of the self-assembly and the equilibrium structure.