Continuous control of a resistance in Co-rich amorphous ferromagnetic microwires during DC Joule heating

In this paper, we present the resistance measurements of the amorphous ferromagnetic Co-rich microwires (metallic nucleus diameters 15-30 μm) during Joule heating by direct current. The heating currents were provided by a programming power supply, which allowed setting up a different heating and cooling regimes. The Wheatstone bridge circuit was used for continuous resistance monitoring during the heating process. We observed the dependences of the microwire resistance versus the time and the applied power of heating for the samples having common composition Co69Fe4Cr4Si12B11 and different diameters. It was shown that the irreversible changes of the microwire resistance were occurred during heat treatment. The microwires have gone through a crystallization phase under linear varying power in the range between 0 and 4.5 W and their relative resistance reduced by up to 10% relative to the initial values. The one-time annealing run increases the relative resistance of the microwires samples from 0.1% to 1% at the various values of maximum power. The repeated heating processes result to the reversibility of the resistance values; in that case each value of maximum applied power provides finite rise of the microwire resistance value.