Nonhysteretic M-H loops in amorphous ribbons carrying alternating currents

The perpendicular field H/sub p/ generated by direct current J/sub d/ usually shifts and narrows the M-H loops of amorphous ribbons that cannot produce zero coercive field H/sub c/ because of enhanced pinning of domain walls at elevated H/sub P/. The enhanced pinning inhomogeneity /spl Delta/S (the difference in strength of pinning close to the opposite faces of the ribbon) can however be used in order to obtain zero H/sub c/ by means of an alternating current or current pulses. When H/sub p/ has nonvanishing projections P on the magnetizations of domains responsible for H/sub c/, H/sub c/=0 occurs for P=S/sub u/ (S/sub u/ is the strength of the weakest pinning centers associated with He) at zero applied field H. Since /spl Delta/S can be simply controlled (e.g. by applying stress on magnetostrictive alloys) zero H/sub c/ can be obtained for almost any material over sizable range of frequencies and amplitudes of H. Some examples are given in the paper.