Magnetic structuring of electrodeposits.

Metal electrodeposition reflects the pattern of the magnetic field at the cathode surface created by a magnet array. For deposits from paramagnetic cations such as Co²⁺ or Cu²⁺, the effect is explained in terms of magnetic pressure which modifies the thickness of the diffusion layer, that governs their mass transport. An inverse effect allows deposits to be structured in complementary patterns when a strongly paramagnetic but nonelectroactive cation such as Dy³⁺ is present in the electrolyte, and is related to inhibition of convection of water liberated at the cathode, in the inhomogeneous magnetic field. The magnetic structuring depends on the susceptibility of the electroactive species relative to that of the nonelectroactive background.