Helical shell-domain structure in laser-annealed Co-based amorphous microwires analyzed by giant magnetoimpedance

A commercial glass-covered, Co-based amorphous microwire (Co67FC3.8Ni1.4B11.5Si14.6Mo1.7) is etched in order to remove its glass cover in a 60.51% hydrofluoric acid solution, and annealed in air by illuminating with a pulsed Nd:YAG laser beams with an energy E of 48 mJ/pulse. Giant magnetoimpedance (GMI) profiles at a frequency f are measure d as function of the angle 0 of the external field, H, with respect to the wire axis. The sign of the H values at the peak of the GMI profiles for f = 100 kHz and at the dip of the GMI profiles for f = 10 MHz, H-p and H-d, respectively, change at theta = 85-90degrees, reflecting that the tilt angle of the helical domains is between 0degrees and 5degrees from the circular direction for the as-etched samples. The variations of H-p and H-d with 0 for the sample with E = 48 mJ/pulse and H-a = 20 Oe show a change in sign of H-p and H-d at theta = 90-100degrees, reflecting that the tilt angle of the helical domains is decreased by about -10degrees compared to that of the as-etched sample. degrees 2002 Elsevier Science B.V. All rights reserved.