Effects of Gamma Irradiation and Thermal Annealing on the Co-Based Amorphous Ribbon

The effects of annealing and gamma irradiation on the magnetic properties of amorphous Co
₆₆
Fe
₄
B
₁₅
Si
₁₅
alloys have been investigated by means of the changes in the giant magneto-impedance (GMI). The results show that there are no differences in the shape of the GMI curves for the samples which are as-quenched, annealed, gamma irradiated, and gamma irradiated after annealing. The GMI ratio showed drastic change according to the sample histories, the GMI ratio drastically increased in the annealed sample compared to as-quenched state, and this increase was recovered considerably by gamma irradiation, but no changes were observed in the as-quenched samples by gamma irradiation. These changes of GMI ratio with sample histories explained in terms of magnetic softness and the fluctuation of the circumferential/transverse anisotropy by gamma heating.