Magnetization reversal behavior in an amorphous alloy

Metglas amorphous Fe-Ni base alloy ribbons supplied by Allied Chemical Co., Morristown, N.J., while mechanically strong, are magnetically very soft, with Hcaround 20-100 mOe. About 20 Oe H is necessary to saturate the material in strip form. The remanence is on the order of 1/3 the saturation. Elastic tensile stress of a few N/mm²greatly increases the magnetization in low fields. The stress resulting from winding the ribbon into a toroidal sample changes its behavior, giving a much slower approach to saturation and an increase in Hc. Thus properties achieved in a strip cannot be maintained on simply winding it into a toroid. Reversal takes place in a series of discontinuous jumps, at fields depending on the previous magnetizing field, just as in cobalt-rare-earth particles. Elastic torsion greatly increases Hcand produces a perfectly rectangular loop, again characteristic of nucleation-dominated reversal.