The electrodeposition of high performance ferromagnetic cobalt-samarium alloys

Co-Sm permanent magnets, such as SMCo5 and Sm2Co 17, are well known for their high coercivity and energy product. More recently, Co-Sm thin films have been studied for the interest in high density recording media and MEMS applications. These films have been prepared by sputtering, evaporation and plasma spraying. However, high manufacturing costs of these processes have limited usage of Co-Sm thin films for consumer electronic devices.;Development of an aqueous electrodeposition continuous process for Co-Sm thin films would provide substantial reduction in manufacturing costs. Initially the Hull cell was used as a screening device to study the dependence of plating variables on Co-Sm electrodeposition from aqueous solution. Systematic parametric studies of DC and PC electrodeposition by parallel electrodes have been performed to study the effects of operating conditions and solution compositions on deposit composition, structure and properties. Relationships between deposit characteristics and magnetic behavior were developed.;Alloy composition appeared strongly dependent on operating conditions and solution components. Addition of glycine suppressed the deposition of hydroxides/oxides and enabled the co-deposition of Sm and Co. High Sm content (32at%) Co-Sm alloys have been obtained from a bath consisting of 1M Sm sulfamate, 0.05M Co sulfate and 0.15M glycine by DC electrodeposition satisfying the stoichiometric compositions of intermetallic Co-Sm alloys of Sm2 Co17 (10.5at%) and SmCo5 (16.7at%). Therefore, CoSm alloys of sufficient Sm content for Sm Co magnets have been achieved by electrodeposition. PC is superior than DC electrodeposition for metallic deposits can be obtained at room temperature without the appearance of hydroxides. The structures of electrodeposited Co-Sm crystallites were dominated by hcp phases. Crystalline properties of deposits strongly depend on Sm deposit content. Increased Sm content changed deposits from crystalline to non-crystalline structures and resulted in smaller particle size and microcracks. Magnetic behavior of deposits showed significant dependence on crystal properties and Sm content. Saturation magnetization decreased with increased Sm content in agreement with sputtered Co-Sm alloys. Increased Sm content led to decreased perpendicular coercivity and squareness changing deposit magnetic properties from anisotropic to isotropic.