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 Hk values) in the ribbon microwave annealed for 45 min at 400 °C resulted in (MI)m reaching its highest value in the ribbons investigated.