Annealing effects on the microwave permittivity and permeability properties of Fe₇₉Si₁₆B₅ microwires and their micowave absorption performances

This paper reports that amorphous magnetic microwires (Fe₇₉Si₁₆B₅) have been fabricated by a melt-extraction technique and have been annealed at 600℃ and 750℃ respectively. Differential scanning calorimeter measurements show that nanocrystalline magnetic phase (\alpha-Fe) has been formed in the amorphous matrix when it was annealed at 600℃. Hard magnetic phase (Fe₂B) was formed in the microwires annealed at 750℃, which increases the magnetic coercivity. Microwave permittivity and permeability are found to be dependent on the microstructures. The permittivity fitting results show that multi Lorentzian dispersion processes exist. For microwires annealed at 750℃, their resonance peaks due to the domain wall movements and natural resonance are found higher than those of microwires annealed at 600℃. The microwave absorption performance of microwires annealed at 600℃ is found better than microwires annealed at 750℃.