Thermal stability of softmagnetic properties of Co-(Nb,Ta)-(Zr, Hf) films with high saturation magnetization

Thermal stability of softmagnetic properties of amorphous Co-(Nb,Ta) - (Zr,Hf) systems with high saturation magnetization (4πMs) was studied. It was found that Hf-containing films, especially Co88Ta8Hf4alloy, with high 4πMs(∼ 10000 Gauss) as high as that of Sendust alloy were thermally very stable even up to 500°C, while the conventional Co-based amorphous films with the same 4πMscould not tolerate such high temperature annealing because of crystallization. The relation between the structural changes and the magnetic properties of Co83(Nb,Ta)13Zr4film (with 4πMs∼8500 Gauss) was also investigated. These films have promising properties as magnetic head core materials for high performance VTR since they can cope with high coercivity media and withstand high temperature fabrication processes.