Temperature dependence of the off‐diagonal magnetoimpedance in sensor configuration utilizing Co‐rich amorphous wires

Abstract

For sensor operation, the temperature stability is of primary importance. In this work, we have investigated the temperature dependence of the magnetoimpedance (MI) in glass‐coated Co‐based amorphous wires which are widely used as MI sensing elements. The magnetic alloy has high Curie and crystallization temperatures, yet, the MI change at moderate temperatures of 20–90 °C and low‐magnetic fields can be about 100%. This is explained by high‐temperature sensitivity of the residual stress due to fast solidification and the difference in thermal expansion coefficients of glass and metal. To reduce the temperature effect, annealing treatment was proposed and applied to the whole sensing element in off‐diagonal configuration comprising the MI wire and detection coil. Annealing treatment at a temperature of 160 °C during 2–3 min makes it possible to significantly improve both the magnetic field sensitivity and temperature stability. After annealing, the output voltage sensitivity in the linear region (±0.7Oe) increases more than 2.5 times and shows little variations with temperature up to 90 °C. For higher magnetic fields, the MI profile still shows noticeable change with temperature: the maximum of the output voltage decreases at a rate of about 0.15%/°C as the temperature is increased. After optimum annealing, the MI curves become almost symmetrical suggesting that a well‐defined circumferential anisotropy is established.

Soft Magnetic Amorphous Microwires for Stress and Temperature Sensory Applications

“…Many FeCo-rich amorphous alloys have a high Curie temperature Tc above 300 ℃ [54], but the magnetic structure of microwires produced from these alloys often experiences temperature variations at much lower temperatures below 80 ℃ [38,46,55,56,57,58,59]. This temperature influence is related with the internal stress relaxing and the corresponding transformation in the magnetoelastic anisotropy.…”

Optimization of temperature stability and sensitivity of the giant magnetoimpedance effect in meander shaped Co-based amorphous ribbon using DC-biased current for sensor application

“…Therefore, temperature stability is a key indicator of performance of GMI sensors, some research on the temperature dependence of GMI in amorphous alloys has been reported [21][22][23][24][25][26][27][28][29]. Methods like conventional [26,30,31] and current annealing [21,32] of the material as well as doping of the material with Cr elements [33] have been done to enhance the GMI temperature stability of amorphous alloys.…”

Magnetic Domain Patterns in Bilayered Ribbons Studied by Magnetic Force Microscopy and Magneto-Optical Kerr Microscopy

“…The amorphous and/or nanocrystalline alloys are deeply examined by many research teams world-wide due to their excellent soft magnetic properties [ 1 , 2 ]. They are produced in many forms and geometries (ribbons, wires, and thin films) by various techniques [ 1 , 3 , 4 ]. Besides other fabrication methods suitable for production of soft magnetic materials the planar flow casting (PFC) is referred to as most utilizable [ 5 ].…”