Electroformed iron and FeCo alloy

Abstract

Iron and FeCo alloys were electroformed from additive-free acidic chloride baths. Film stress and magnetic properties were strongly influenced by deposition current density and operating temperature. In general, low film stress and low coercivity ( H C) was achieved with low current density and high operating temperature baths. SEM micrographs indicated that these conditions promote large grain growth. Coercivity of electroformed iron films linearly increased with increasing film stress, indicating that magnetoelastic energy is a dominant anisotropy. The addition of 0.25 M CaCl 2 improves current efficiency while maintaining low film stress. The lowest iron film stress of 5 MPa was achieved from 1.5 M FeCl 2 in the absence of CaCl 2 at 20 mA cm −2 with a current efficiency of 91%. A “normal” codeposition of FeCo was observed in acidic chloride baths, where the deposition rate of Co 2+ was faster than Fe 2+. Film compositions also played an important role in magnetic properties of FeCo films in addition to film stress. Magnetic saturation ( M S) of FeCo films increased linearly with an increase in deposited Fe content. High magnetic saturation with low-stress ( M S of 2.3 T and σ=70 MPa) were achieved from 71Fe29Co films.