Neutron reflectivity of electrodeposited thin magnetic films

• Published in: Electrochimica acta 2014-08, Vol.138, p.56-61
• Main Authors: Cooper, Joshaniel F.K., Vyas, Kunal N., Steinke, Nina-J., Love, David M., Kinane, Christian J., Barnes, Crispin H.W.
• Format: Article
• Language: English
• Subjects: Cobalt; Copper; Magnetic Thin Films; Multilayers; Neutron Reflectivity
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2014.06.086

•Electrodeposited magnetic bi-layers were measured by polarised neutron reflectivity.•When growing a CoNiCu alloy from a single bath a Cu rich region is initially formed.•This Cu rich region is formed in the first layer but not subsequent ones.•Ni deposition is inhibited in thin film growth and Co deposits anomalously.•Alloy magnetism and neutron scattering length give a self-consistent model. We present a polarised neutron reflectivity (PNR) study of magnetic/non-magnetic (CoNiCu/Cu) thin films grown by single bath electrodeposition. We find that the composition is neither homogeneous with time, nor consistent with bulk values. Instead an initial, non-magnetic copper rich layer is formed, around 2nm thick. This layer is formed by the deposition of the dilute, but rapidly diffusing, Cu2+ ions near the electrode surface at the start of growth, before the region is depleted and the deposition becomes mass transport limited. After the region has been depleted, by growth etc., this layer does not form and thus may be prevented by growing a copper buffer layer immediately preceding the magnetic layer growth. As has been previously found, cobalt deposits anomalously compared to nickel, and even inhibits Ni deposition in thin films. The layer magnetisation and average neutron scattering length are fitted independently but both depend upon the alloy composition. Thus these parameters can be used to check for model self-consistency, increasing confidence in the derived composition.