Method for evaluating the temperature of amorphous ferromagnetic microwires under Joule heating

•The Co69Fe4Cr4Si12B11 microwire under heating up to 600 °C become crystallized.•Studies of microwire’s resistance when heated in a furnace and by the Joule heating.•Temperature dependence of the resistance of the crystallized microwire becomes linear.•Calibration dependence of the microwire’s temperature on the Joule heating power.•Control of temperature and resistance of microwire at different Joule heating modes. The results of comparative studies of the electrically conductive properties of Co69Fe4Cr4Si12B11 glass coated amorphous microwires obtained during their heat treatment in a conventional furnace and by the Joule heating method are presented. The fully crystallized microwire dramatically changes its electrically conductive properties. We found that the crystallized microwire has a temperature coefficient of resistance, α = 315*10-6 1/ °C. The crystallized microwire was used as a reference resistance thermometer under Joule heating for determining the temperature of the microwire as a function of the applied thermal power T(P). This dependence obtained was used to determine the temperature dependence of the resistance RM(T) of other microwire samples in an amorphous or partially crystallized state of the same series. The proposed method allows to select thermal modes during Joule annealing of microwires and to compare the resistive, magnetic and structural-phase properties of microwires after thermal effects.