Magnetoimpedance studies on laser and microwave annealed Fe₆₆Ni₇si₇B₂₀ ribbons

Magnetoimpedance (MI) has been investigated in the laser and microwave annealed Fe₆₆Ni₇Si₇B₂₀ ribbons. The largest MI [(MI)_m] values of the ribbons annealed using laser with energies of 150, 200 and 250 mJ/pulse (mJp) are 25% (at 7 MHz), 30% (at 5 MHz) and 21% (at 7 MHz) respectively. The effect of domain wall pinning on MI was observed as field insensitive regions in the MI profiles in the ribbon annealed using 150 mJp energy. Flower shaped grains in amorphous matrix in the ribbon annealed with 200 mJp energy are responsible for highest (MI)_m due to the least anisotropy. In the ribbons annealed for 40, 45 and 50 min at 400 °C using microwaves, (MI)_m values are 35% (at 5 MHz), 46% (at 6 MHz) and 29% (at 7 MHz) respectively. The large DC conductivity and the least anisotropy (smallest H_k values) in the ribbon microwave annealed for 45 min at 400 °C resulted in (MI)_m reaching its highest value in the ribbons investigated. - Highlights: • Magnetoimpedance studied on Fe₆₆Ni₇Si₇B₂₀ ribbons annealed using laser/microwaves. • Domain wall pinning observed in the ribbon annealed with 150 mJ/pulse of laser. • Flower shaped grains observed in the ribbon annealed with 200 mJ/pulse of laser. • Large magnetoimpedance and least anisotropy observed in the above ribbon. • Microwave annealed ribbons exhibited conductivity-magnetoimpedance correlation