We provide new experimental studies of the temperature dependence of the giant magnetoimpedance (GMI) effect and hysteresis loops of Fe-rich and Co-rich amorphous microwires with rather different room temperature magnetic properties and GMI effect features. We observed a remarkable modification of hysteresis loops and magnetic field dependence of the GMI ratio upon heating in both of the studied samples. We observed a noticeable improvement in the GMI ratio and a change in hysteresis loops from rectangular to inclined upon heating in Fe-rich microwire. However, the opposite trend was observed in Co-rich microwire, in which, upon heating, the shape of the hysteresis loop changed from linear to rectangular. Generally, the evolution of the shape of the hysteresis loops during heating correlates with the modification of the dependencies of the GMI ratio ΔZ/Z on the magnetic field. For Co-rich microwire, the double-peak magnetic field dependence changed to single-peak, while for Fe-rich microwire, the opposite tendency was observed. The origin of the observed temperature dependences of the hysteresis loop and the GMI effect is discussed, considering internal stresses’ relaxation during heating, the temperature dependencies of the magnetostriction coefficient, and internal stresses, as well as the Hopkinson effect.

We studied the effect of heating on the magnetic properties and giant magnetoimpedance (GMI), effect of Co69.2Fe3.6Ni1B12.5Si11Mo1.5C1.2 glass-coated microwires with vanishing magnetostriction. We observed, that upon heating the hysteresis loop changed its shape from inclined to rectangular. These changes in hysteresis loop shape correlate with modification of magnetic field dependencies of GMI ratio, ΔZ/Z, from double-peak to single-peak and with change in value of maximum GMI ratio. The origin of the observed changes in the hysteresis loop and the GMI effect is discussed in terms of the Hopkinson effect, internal stresses relaxation upon heating, and the temperature dependencies of internal stresses and the magnetostriction coefficient.