Determination of diffusion in electrodeposited Cu-Ni compositionally-modulated multilayers based on magnetic measurements

The thermal stability in compositionally-modulated metallic multilayers (CMMs) is an important limitation towards their application. In the case of CMMs consisting of an alternation of magnetic and non-magnetic sublayers, the particular magnetic properties are destroyed by the diffusion between the sublayers. A method for the study of the diffusion in magnetic CMMs, based on the decrease in magnetisation with time and temperature,is presented. Systematic measurements of the magnetisation after proper heat treatment, by means of a Curie-Faraday microbalance, allow a complete characterisation of the diffusion process within the CMMs. Experimental results are presented on electrolytic Cu-Ni CMMs with 100 nm thick sublayers. The value obtained for the activation energy agrees well with published data on diffusion of Cu in Ni obtained by radioactive measurements.