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 (ΔZ/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 100 deg. C for 30 min, attributed to maximum value of the circular permeability achievable for the circumferential domain configuration. Higher temperature annealing (between 125-300 deg. C) modifies the values of circular permeability for the circumferential domain configuration, resulting in lowering of (ΔZ/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