Temperature Dependence of Magnetization Reversal and Harmonic Spectrum in Low Curie Temperature Amorphous Microwires

The present study focuses on the investigation of the magnetization reversal process in amorphous microwires of the composition Co_64.82Fe_3.9B_10.2Si₁₂Cr₉Mo_0.08, which possesses a low Curie temperature ${{T}_c}$ of 61 °$\mathrm{C}$. The microwire retains a nearly rectangular hysteresis loop, an axial anisotropy, and a positive magnetostriction up to ${{T}_c}$. The coercivity decreases with temperature, following the decrease in the saturation magnetization ${{M}_s}$, but it has a different dependence on ${{M}_s}$ far from and near $\ {{T}_c}$, which suggests different mechanisms of magnetostriction in these temperature intervals. Furthermore, the harmonic spectrum of the voltage induced during remagnetization is also temperature sensitive. The area under the voltage pulse is directly proportional to ${{M}_s}$, resulting in a comparable dependence of the harmonic amplitudes. In the context of potential applications in wireless temperature sensors, measuring the harmonic spectrum offers distinct advantages based on lock-in techniques. In addition, the temperature range over which the harmonic spectrum varies most is extended by using two (or potentially few) microwires with different ${{T}_c}$. The change in ${{T}_c}$ from 61 °$\mathrm{C}$ to 57 °$\mathrm{C}$ is achieved by current annealing of the same microwire, which helps to extend the temperature-sensitive range of the two microwire harmonic responses between 40 °$\mathrm{C}$ and 61 °$\mathrm{C}$.