ORIGIN OF ZERO-LOSS M-H LOOPS IN AMORPHOUS RIBBONS CARRYING AN AC CURRENT

M-H loops with a vanishing coercive field H(c) and loss E have been ob tained for an amorphous Co70.3Fe4.7Si15B10 ribbon carrying an ac curre nt of appropriate amplitude, frequency, and phase. The actual shape of the ac-current pulse is immaterial as long as the phase and amplitude remain the same. The phenomenon is explained within the framework of the recent model for the magnetization of a ferromagnetic ribbon carry ing a dc current. The general condition for the occurrence of H(c) = 0 is derived and some applications of the phenomenon are discussed.