Magneto-impedance measurements in amorphous Co-based magnetic wires at high frequency

An alternative method to evaluate the magnetic response of soft magnetic systems in the high-frequency region (1 MHz-6 GHz) is presented here. The proposed experimental set-up is based on the measurement of the four scattering parameters S(ij) of a coaxial line by means of a vectorial network analyzer. The magnetic sample, either in wire or ribbon form, is used as the inner conductor of a coaxial line. The characteristic impedance of the line section is given by an analytical formula taking into account the geometrical structure of the device and the sample physical properties. Transmission line theory has been successfully employed to extract from the raw experimental data the information concerning the magnetic sample, discarding the contribution of the terminations. Magneto-impedance is obtained by measuring the characteristic impedance under different applied magnetic fields. The proposed method provides a natural extension of the usual characterisation techniques from lower frequencies up to 6 GHz. As an example, the magneto-impedance response of Co-based amorphous and glass-covered wires in the high-frequency region will be discussed. (C) 2002 Elsevier Science B.V. All rights reserved.