Magnetic-field effects on fractal electrodeposits

A uniform magnetic field unexpectedly alters the form of copper deposits gr own in a flat electrochemical cell; the patterns change from radial to unid irectional when the cell is horizontal and vice versa when the cell is vert ical. The electrodeposits are characterised by their chirality and fractal dimension. Complex impedance spectra show that the effective diffusion coef ficient of the copper ions is doubled in a field of 1 T. The results demons trate that the field produces a body force comparable to that of gravity. F rom dimensional analysis, it is inferred that the field modifies convective flow on a scale of a few microns close to the cathode.