Magnetoresistance Controls Arboreous Bead-Dendritic Growth of Magnetic Electrodeposits: Experimental and Theoretical Results

The effect of magnetic fields applied on magnetic metals electrodeposition was examined. Nickel deposits obtained from a Watt solution with coumarin, at cathodic potentials of -1000, -1200, and -1300 mV/SCE, without and with, both, perpendicular and parallel oriented to the electrode surface low applied magnetic fields (up to 500 Oe) were examined by scanning electron microscopy (SEM) technique. At a potential of -1300 mV/SCE, a dramatic difference was observed between nickel morphologies obtained with a perpendicular oriented magnetic field (zero MHD effect) and those obtained in the absence of one. The nickel deposit obtained with perpendicular oriented magnetic fields was a very developed 3D arboreous-bead-dendritic structure. On the other hand, the nickel deposit obtained without the presence of magnetic field was very rough, with a clearly visible clustered structure. The obtained nickel morphologies are then compared with copper morphologies. Based on the fact that copper deposits obtained with and without a perpendicular oriented magnetic field were dendritic structures, the observed difference between nickel deposits with and those without a perpendicular oriented field, is essentially ascribed to the magnetoresistance effect on the magnetic deposits, which are nonexistent in nonmagnetic materials. We also have done experiments with iron deposits