Structure and Giant Magnetoresistance of Co-Fe/Cu Multilayer Films Electrodeposited from Various Bath Formulations

Abstract

Detailed new results are reported on the preparation and giant magnetoresistance (GMR) of electrodeposited Co-Fe/Cu multilayer films by using four different baths (sulfamate, sulfate, ammonium chloride and sodium citrate type solutions). Two-pulse plating was applied for Co-Fe(5nm)/Cu(5nm) multilayer preparation by using galvanostatic pulses for the deposition of the magnetic layer. The Cu layer deposition potential was electrochemically optimized for each bath formulation by analyzing the current transients during the deposition of the non-magnetic layers. The optimal Cu deposition potential was found to be dependent both on the bath formulation and the Fe2+/Co2+ ion concentration ratio. The results of X-ray diffraction (XRD) measurements were in agreement with the composition of the samples. At low Fe content (about 10 at.% Fe) in the magnetic layer, an fcc structure was formed (in some cases, even multilayer satellites were observed). In samples with high Fe content (about 33 at.% Fe) in the magnetic layer, both fcc and bcc phases were present. A GMR behavior was observed for all multilayers, with a maximum GMR of about 4% in some cases. For multilayers from the sulfamate, sulfate and chloride baths, the GMR exhibited a multilayer-type behavior whereas the GMR of samples from the citrate bath was rather similar to the behavior of granular magnetic alloys containing also superparamagnetic regions.