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 the as-quenched and microwave annealed amorphous Fe73.5Nb3Cu1Si13.5B9 ribbon as a function of biasing d.c magnetic fields (-60 to +60 Oe) and excitation frequencies (0.1, 1, 10 and 20MHz). The magneto-impedance (both components) response was much reduced for the microwave annealed ribbon and the changes were more discernable at higher excitation frequencies. The imaginary component of magneto-impedance showed maxima at finite (non-zero) d.c magnetic fields for both the as-quenched and microwave annealed ribbons. Magnetization measurements performed for both the as-quenched and microwave annealed ribbons revealed the magnetic hardness of the latter. The initial susceptibility decreases by two orders of magnitude for the microwave-annealed ribbon. XRD measurements indicated the transformation of the surface of the ribbon from the amorphous state to the crystalline one.