Stress in electrodeposited CoFe alloy films

CoFe alloys with 50–70% Fe have the highest magnetic moment of 2.4 T. There have been numerous research and development studies dedicated to achieving 2.4 T soft magnetic films by electrodepositing CoFe and CoFeNi alloys. The high tensile stress of the electrodeposited high moment films is one of the key causes slowing down the implementation of CoFe alloys. There have been few reported studies on the structure and stress evolution during the deposition of CoFe film either by vacuum processes or solution processes. This work reports on the preliminary finding related to the tensile stress in electrodeposited CoFe films as a function of grain size, alloy composition, and other deposition parameters. The residual tensile stress was found to increase with decreasing grain size in the film, which was accompanied by the increase of iron content in the films. Pulse plating study demonstrated to have little effect on film stress. Solution temperature was found to be highly effective in reducing tensile stress in the film, which is speculated to be attributed to the increased grain size from elevated deposition temperatures.