Influence of microwave annealing on GMI response and magnetization of an amorphous Fe73.5Nb3Cu1Si13.5B9 ribbon

The resistive and reactive components of magneto-impedance was studied for as-quenched and microwave annealed amorphous Fe73.5Nb3Cu1Si13.5B9 ribbons as functions of biasing d.c magnetic fields (ranging from −60 to +60 Oe) and excitation frequencies (0.1, 1, 10 and 20 MHz). The magneto-impedance response was much reduced for the microwave annealed ribbon and the changes were more observable at higher excitation frequencies. The reactive component of magneto-impedance exhibited a peak at higher frequencies for both the as-quenched and microwave annealed ribbons. Magnetization measurements revealed the occurrence of magnetic hardness of the ribbon after microwave treatment. XRD measurements indicated the transformation of the surface of the ribbon from the amorphous state to the crystalline one.