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 (4πM
s
) was studied. It was found that Hf-containing films, especially Co
88
Ta
8
Hf
4
alloy, with high 4πM
s
(∼ 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 4πM
s
could not tolerate such high temperature annealing because of crystallization. The relation between the structural changes and the magnetic properties of Co
83
(Nb,Ta)
13
Zr
4
film (with 4πM
s
∼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.