Magnetic CoNi alloys were electrodeposited from chloride baths to investigate the influence of saccharin on thin film stress. As the Co2+ concentration in the plating solution was increased, the stresses in the CoNi thin films increased. CoNi thin films electrodeposited from chloride baths without saccharin exhibited increased tensile stresses (from 145 to 270 MPa) with increasing Co concentration in the plating baths, whereas CoNi thin films electrodeposited with saccharin showed decreased stress. Notably, CoNi thin films deposited with saccharin showed the transition from compressive to tensile stress modes (-85 to 120 MPa) with increasing Co2+ concentrations. (C) 2004 The Electrochemical Society.