Microelectrodeposition of Co–Pt alloys for micromagnetic applications

Abstract

Miniaturisation of advanced devices, such as sensors and micromotors, requires the development of micromagnets of small size but with a high magnetostatic energy. Cobalt alloys, and in particular cobalt–platinum alloys, are proposed for such applications, as well as for magnetic recording, due to their magnetic and corrosion resistance properties. Such alloys can be electrodeposited with good magnetic properties at high thickness by addition of phosphorus and other elements that favour a stable growth of the microstructure during deposition. Results on electrodeposition of Co–Pt–W(P) and Co–Pt–Zn(P) layers from sulphamate citrate solutions are presented. Thick deposits of high coercivity and layers with different preferred orientation are obtained by changing the operation conditions. The deposits have magnetic anisotropy, which favours their implementation in magnetic circuits where the field is perpendicular or parallel to the surface: in the former case, the magnetic easy direction of cobalt alloys must be perpendicular to the surface and in the latter, it must be parallel to the surface. The magnetic properties of Co–Pt-based alloys can be tailored to obtain the desired magnetic properties in relation to the application envisaged.