THE REMAGNETIZATION PROCESS IN THIN AND ULTRA-THIN FE-RICH AMORPHOUS WIRES

A comparative study of the remagnetization process of highly-magnetostrictive as-cast Fe-rich amorphous wires having different diameters (from 165 to 10 mu m) and lengths (between 10 cm and 2 mm) is here reported for the first time. Wires obtained by conventional in-rotating-water quenching (165 down to 70 mu m diameter) and by a modified Taylor's technique (2.5 mu m glass cover on 10 to 15 mu m diameter magnetic core) are studied. Macroscopic and local hysteresis loops are measured by induction technique with the help of large and very tiny pick up coils respectively. From the latter, the magnetization profile of these magnetically bistable wires is determined. The critical length to observe a single and large Barkhausen jump when remagnetizing decreases with the diameter of the sample. In particular, for the wires covered by glass the critical length to observe spontaneous bistability is less than 2 mm. Values of those critical lengths are interpreted taking into account the compromise between magnetostatic and magnetoelastic energy terms.