Effects of torsion on the magnetoimpedance response of CoFeBSi amorphous wires

CoFeBSi amorphous wires prepared by the in-rotating-water quenching techniq ue were submitted to torsion annealings by Joule heating. Their impedance r esponse, Z. was measured in the giant magnetoimpedance arrangement in the 5 Hz-13 MHz frequency range and 0.2-22 mA AC current amplitude. By compariso n with as-cast wires of the same composition. a decrease in Z and an increa se in the field irreversibility (at I MHz and 2 mA) were observed when subm itted to axial DC magnetic fields of + 40 Oe. The analysis of the real and imaginary components of inductance at f < 500 kHz allowed the resolution of domain wall bulging from domain wall displacement, As compared with as-cas t wires., torsion annealing produced a decrease in both processes. These re sults are consistently interpreted in terms of an induced magnetic anisotro py. (C) 2001 Elsevier Science B.V. All rights reserved.