Temperature offset drift of GMI sensors

Temperature offset stability of magnetoimpedance sensor is discussed based on experiments accomplished with soft magnetic amorphous material. An amorphous ribbon of Co67Fe4Cr7Si8B14 composition was tested in a magnetic shield with adjustable internal temperature. DC resistance and complex components of impedance at frequencies up to 30 MHz were investigated in the temperature range of −20 to +75 °C. The measured data were used for the evaluation of temperature dependence of transverse permeability that is assumed to be a major contributor to the temperature variations of impedance. We also show that thermal treatments of the amorphous ribbon significantly affect the temperature behaviour of GMI. In case of tested alloy, which has very small negative temperature coefficient of resistivity, the achieved equivalent temperature offset drift is −0.27 A/m/K (−340 nT/K).