Thermal stability of giant magneto-impedance effect in glass-covered amorphous wires

Thermal stability of Giant magneto-impedance (GMI) effect of Co-based amorphous glass-covered wires was investigated. The temperature measurement was conducted in a special calorstat cell between 25°C and 200°C, and the GMI effect of the as-cast, glass-removed and DC annealed wires was measured at 100kHz-12MHz ranging from 0Oe to 80Oe. Experimental results show that the ambient temperature has a significant influence on the thermal stability of GMI effect, it is caused by external conditions: driving frequency, magnetic field and sample states. The thermal stability and GMI fluctuating variation at different temperature of three-type wires could be quantificationally characterized by GMI ratio variation difference Δ[δZ/Z _max]_max^T of three-type wires, and drastically improved with the driving frequency increasing to 10MHz, and the working range of magnetic field for possible sensor applications should be below 10Oe. While there is different from as-cast and glass-removed wires, DC annealed wire has twin-working-zone range (relatively low field 0Oe-2Oe & relatively high field 2Oe-10Oe) of magnetic field at relatively high frequency (10MHz) for sensor applications with different detection range of weak magnetic field. So, the improved thermal stability is caused by the co-actions of remarkable skin-effect, magnetic polarization and magneto-crystalline anisotropy energy with the increasing frequency. It therefore is concluded that the optimal driving frequency of 10MHz and the detection range of weak magnetic field (2Oe-10Oe) is favorable for the design parameters choices of high-performance GMI sensor.