(Invited) Magnetic Gradient-Assisted Physical and Chemical Structuring of Electrodeposits

Magnetic thin films, micro and nano structures are key features in magnetic sensors and for data storage in hard drives. To date often physical deposition methods are more frequently employed than electrodeposition to produce these magnetic structures. This is due to the fact that the usually inexpensive alternative production by electrodeposition requires sophisticated masking or templating if structured deposits are desired. Magnetic-field assisted electrodeposition has been demonstrated as a method to produce structured deposits by employing reusable magnetic gradient templates. [1] The working principle is based on a locally enhanced mass transports thanks to a magnetic gradient force induced local convection in the electrolyte during electrodeposition. In regions of high magnetic gradients, typically film thickness and roughness are increased for paramagnetic ions like Cu 2+ , Co 2+ or Fe 2+ . Here, we demonstrate that not only single component metals, but also bimetallic alloy electrodeposits can be deposited in a desired structure by this approach. By suitably selecting the electrolyte composition and deposition parameters, we demonstrate that the current efficiency can be increased for the electrodeposition of transition metal-based alloys. This is evidenced by electrochemical quartz crystal microbalance studies during electrodeposition of CoFe in the presence of varied magnetic gradients. [2] In addition, we show that also chemical structuring of bimetallic deposits can be achieved by means of magnetic gradient-assisted electrodeposition, which is shown or CuNi electrodeposits. For both systems the observed local morphological and compositional changes are characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. The experimental findings are then discussed in terms of magneto-hydrodynamic effects, which are attributed to the magnetic field gradient force. Thus, magnetic-gradient assisted electrodeposition is suggested as a new route to magnetic patterning of surfaces. [1] Tschulik, Kristina; Koza, Jakub Adam; Uhlemann, Margitta; Gebert, Annett; Schultz, Ludwig Electrochemistry Communications , 2009 , 11 (11), 2241–2244 [2] Karnbach, F.; Uhlemann, M.; Gebert, A.; Eckert, J.; Tschulik, K. Electrochimica Acta , 2014 , 123 , 477–484