High frequency magnetoimpedance in amorphous Co71Fe4B15Si10 ferromagnetic alloy

Room-temperature giant-magnetoimpedance is a magnetotransport effect occuring in soft materials either in ribbon, thin film, fiber or wire form. High frequency magnetoimpedance measurements reaching a maximum value of 5 GHz have been performed on melt spun Co71Fe4B15Si10 ribbons. The samples have been submitted to various thermal treatments al suitable temperatures under a saturating transverse magnetic field. To perform these measurements, an adhoc cell has been developed based on a standard electromagnetic transmission line. In this paper are reported and discussed the results of magnetoimpedance measurements performed both as a function of the frequency and of the magnetic field strength. Finally the dependence of magnetoimpedance on annealing conditions is presented.