Influence of thermal annealing on magnetoimpedance in glass-covered Co-B-Si-Mn microwires

Influence of thermal annealing on magnetoimpedance response and its sensitivity to magnetic field in amorphous Co83.2B3.3Si5.9Mn7.6 glass-covered microwire is investigated. Thermal annealing influences the circumferential domain structure thus affecting the magnetoimpedance ratio and its sensitivity to the magnetic field. Maximum magnetoimpedance ratio (DeltaZ/Z)(max) up to 50% and the sensitivity to magnetic field of 7.4%/Oe at 5 MHz is obtained in the microwire annealed at 100degreesC for 30 min, attributed to maximum value of the circular permeability achievable for the circumferential domain configuration. Higher temperature annealing (between 125-300degreesC) modifies the values of circular permeability for the circumferential domain configuration, resulting in lowering of (DeltaZ/Z)(max) and corresponding sensitivity to magnetic field. Possible application of this material is in miniaturized sensor devices, especially for local detection of magnetic fields. (C) 2002 Elsevier Science B.V. All rights reserved.