Laser annealing effect of giant magneto-impedance in amorphous Co66Fe4Nib14Si15 ribbon

The magneto-impedance (MI) profiles of Co66Fe4NiB14Si15 amorphous ribbon varied sensitively with the annealing energy of the pulsed Nd:YAG laser, reflecting the change of anisotropy field which determines the field dependence of transverse permeability. Laser annealing effect of giant magneto-impedance (GMI) in amorphous Co66Fe4NiB14Si15 ribbon are discussed in terms of laser annealing energy. The pulsed Nd:YAG laser was pumped with Kr-lamp and consisted of a Nd:YAG rod of φ 5 mm×70 mm (AR coated plane/plane), a full mirror and output coupler (30% transmission). The wavelength was 1.064 μm and the pulse width was 220 μs. The GMI ratio increases with annealing energy showing largest value at 136 mJ/pulse (peak power is ∼620 W). The GMI ratio decreases with further increment of annealing energy. The decreasing Hk with the annealing energy is ascribed to the increase of magnetic softness, while the increasing Hk and the decreasing MI ratio for the further increment of annealing energy could be due to the microstructural change by the laser annealing.