A study of the incorporation of magnetic barium ferrite microparticles into a CoNi matrix by means of electrodeposition over silicon-base substrates has been performed. A cationic surfactant synthesized in our laboratory (4-ethylazobenzene-4'-(oxyethyl)trimethylammonium iodide -AZTMAI) has been selected to favour the inclusion of magnetic particles in the alloy deposit. This surfactant reduces during the cobalt-nickel electrodeposition avoiding its inclusion in the film and favours the inclusion of magnetic particles without damaging the deposits quality. The amount of ferrite incorporated during the electrodeposition increases gradually with the surfactant concentration. A moderate deposition temperature allows greater barium ferrite incorporation. Magnetic properties of CoNi-barium ferrite deposits obtained in the presence of AZTMAI are clearly different of those corresponding to pure-CoNi films obtained in the absence of surfactant. Coercivity is clearly increased. (C) 2007 Elsevier B.V. All rights reserved.