Electrodeposited cobaltmolybdenum magnetic materials

Cobaltmolybdenum (CoMo) induced electrodeposition has been studied from a sulphate+citrate bath on carbon electrodes, under conditions near to neutral pH. Crack-free homogeneous deposits with a low percentage of molybdenum can be easily obtained from low molybdate concentrations applying low deposition potentials or current densities. The formation of this kind of deposit is related to Qox/Qred around 1 in the voltammetric/stripping experiments. Moreover, percentages of molybdenum up to 60% can be obtained from high molybdate concentrations but, in this case, the deposits show cracks. The formation of these cracked deposits can be predicted from the observed distortions in the j–t and E–t deposition transients. Coatings with a partially amorphous structure, or with a crystalline structure of nanometric crystal size, are obtained. The magnetisation results show that the saturation magnetisation gradually decreases when the percentage of molybdenum increases in the deposit. Simultaneously, a clear decrease of the coercitivity is observed from the lowest percentage of molybdenum with respect to the value of pure cobalt coatings.