Behavior of the amorphous ferromagnetic ribbons in the very low fields

The D.C. and A.C. magnetic properties and loss factors of five Co-based amorphous ribbons with different compositions in the low magnetic fields were measured. The results show that there is a distinct turning field Hp for B(H), μ(Hm) and 2πtan δ/μ−Bm. The existence of Hp can be explained by means of the domain wall pinning effect in the low fields. The measured Hp corresponds to the minimum pinning field (∼10 mOe) in samples. It is suggested that the large gradient of intrinsic stresses in the ribbons is main cause of the low field pinning effect on domain walls; then we obtained a formula for Hp which was estimated to be 2–20 milli-Oersteds.