Measurement and Model of the Tensile Stress Dependence of the Second Harmonic of Nonlinear GMI in Amorphous Wires

The second harmonic component of nonlinear GMI in soft magnetic wires with helical anisotropy and near-zero negative magnetostriction subjected to different tensile stresses is studied for various current amplitudes (3-13 mA_rms) and frequencies (1-3 MHz). In the absence of tensile stress, the dc field dependence of the second harmonic of the voltage across the wire, V_2f, exhibits a symmetric four-peak structure. The application of increasing tensile stress at relatively low current (3-5 mA_rms) causes the V_2f signal to convert to a three-peak structure after a complicated series of changes. The three-peak structure consists of two outer peaks (OP) and one small central peak (CP) situated at very low field. When the current amplitude is increased, the V_2f signal reverts to the four-peak structure, reversing the same steps. At relatively high frequencies, the V_2f signal increases with current amplitude to more than 160 mV at high stress. Using a simple quasi-static model, we were able to qualitatively reproduce the three and four-peak structures and their dependence on current amplitude and tensile stress. Frequency dependence requires a dynamical model, as does precise determination of sizes and positions of peaks. This is being developed