Trinity College Dublin

Electrodeposition is a useful technology for producing metallic films. Magnetic fields have suprising effects on the morphology and rate of growth of electrodeposition, which we investigate using numerical simulation and carefully designed experiments.

 

Mass Transport

A magnetic field is found to enhance the current density j in the deposition of metals like Cu with a B^1/3 variation. This is a consequence of the Lorentz force j x B which induces bulk convective flow, narrowing the diffusion layer at the cathode. The effect is modelled numerically using the finite element hydrodynamics package FLUENT.

 

Morphology

A magnetic field has a dramatic influence on the morphology of 2D fractal electrodeposits shown below. This has been modelled by adapting ‘diffusion limited aggregation’ (DLA) to take account of electric and magnetic fields, gravity and concentration.

No field	Field out of page	Field into page	Field in plane

 

New Alloys

Electrodeposition is used industrially to produce the permalloy (Fe20Ni80) write-head for hard disks. There is a search for new soft ferromagnetic electrodeposited alloys with a much higher polarisation than permalloy. Pulsed electrodeposition is also a way of producing atomic-scale magnetic multilayers. Hard magnets such as CoPt, FePt are electroplated for applications involving microdevices. Electroplating providing lower cost than many alternative techniques, such as sputtering or MBC