Giant magnetoimpedance in amorphous Co83.2Mn7.6Si5.8B3.3 microwires

The magnetoimpedance (MI) of a glass-coated amorphous Co83.2Mn7.6Si5.8B3.3 microwire has been studied up to a frequency of 11 MHz and varying a dc mag netic field (H-dc) within +/- 140 Oe. Giant magnetoimpedance (GMI) effect h as been observed within a frequency range, f similar to 1-8 MHz with a maxi mum change of 53% around 4 MHz. At low frequency (f<6 MHz), maximum value o f MI is observed at H-dc=0 when measured against H-dc whereas high frequenc y (f>6 MHz) results show the appearance of two peaks at nonzero values of H -dc. The effect of axial tensile stress (maximum 566 MPa) and current ampli tude (0.2-5.0 mA) on MI has been studied. The application of external stres s changes the MI results to a large extent whereas almost no change in MI i s observed due to the change in current amplitude. The magnetization of the same sample has also been measured in presence of different tensile stress es to understand the domain structure and magnetoimpedance results. The exp erimental results of GMI have been explained considering the skin effect in the frequency range of MHz. The applied de magnetic field changes the circ ular permeability and the penetration depth of the ac current which in turn changes the impedance of the sample.