Влияние токового отжига на температурные зависимости магнитоимпеданса в аморфных микропроводах

Abstract

Miniaturization of material’s size is the key feature in many technological applications, in particular, in sensor systems. To achieve this goal, Taylor-Ulitovski technique was employed to produce microwires with very small (from 0.2 up to 100 µm) diameters. Ferromagnetic amorphous microwires exhibit giant magnetoimpedance effect (GMI) which is useful to develop high performance magnetic sensors. Since the discovery of GMI, a considerable amount of interest was devoted to enhancing sensitivity with respect to various external stimuli (magnetic field, stress, temperature). On the other hand, GMI sensing elements should have high environment stability. In the present work, a comprehensive study of the temperature effects on the magnetoimpedance behavior in amorphous microwires is conducted. The wires under investigations of the composition Co60.51Fe3.99Cr12.13B13.53Si9.84 have a relatively high Curie temperature (>300 ℃) but may demonstrate considerable temperature dependence in the intermediate temperature range (<100 ℃) of dc and ac magnetic properties. We showed that the as-casted wires exhibited a notable change in magnetic anisotropy, from circumferential to an axial anisotropy, owing to the internal stress relaxation. This is accompanied by huge variation in the magnetoimpedance behavior: the impedance vs magnetic- field plots change shape: from two symmetrical peaks to a single central peak. Current annealing (dc current of 25 mA magnitude for 60 min) was proposed to achieve a thermal stabilization of the magnetization processes and magnetoimpedance in glass-coated amorphous wires.