Magnetically soft and electrically resistive CoNiFeS alloy films prepared by electrodeposition

Magnetic properties of electrodeposited CoNiFeS films were studied to seek their feasibility for applications in microelectromagnetic devices such as high areal density recording heads. We started with NiFe and then expanded experiments to a CoNiFe system. Finally, we added a fourth element, sulfur, to further improve physical properties. A small amount of sulfur inclusion has induced grain size refinement and offered magnetic softness to the film accompanying with increased electrical resistivity. Grain size was found to be in the order of 10 nm. Co73Ni17Fe9S1 (in wt. %) films with thickness of 2.5 mu m exhibit superior properties compared with currently utilized Ni45Fe55: high saturation magnetic flux density (B(s)similar to 17 kG), low coercivity (H(c)similar to 0.4 Oe), near zero saturation magnetostriction (lambda(s)similar to 1.0x10(-6)), high permeability (mu similar to 1300 at 100 MHz), and high electrical resistivity (rho similar to 55 mu Omega cm). From a processing standpoint, we were able to control film thickness uniformity by adjusting current distributions between the auxiliary electrode and cathode across 100 mm wafers. (C) 2000 American Institute of Physics.[S0021-8979(00)73008-8].