Optimization of GMI properties by AC Joule annealing in melt‐extracted Co‐rich amorphous wires for sensor applications

Abstract

We report here on a comprehensive study of an alternatingcurrent Joule annealing (ACJA) method for optimizing the giant magnetoimpedance (GMI) effect of Co-rich amorphous wires for sensor applications. Experimental results indicated that the proper ACJA treatment can drastically improve the GMI property of as-cast wire. At 10 MHz, the maximum GMI ratio [DZ/Z 0 ] max of ACJA-ed wire increase to 205.38%, which is nearly 3.3 times that of 62.84% for as-cast wire, and the maxima field response sensitivity j max of ACJA-ed wire increases to 345.90%/Oe by more than twice that of 170.92%/Oe for as-cast wire. With an increase of AC amplitude, a remarkable dependence of GMI performance appears on the microstructural evolution such as the structural relaxation, the degree of local order, as well as circular magnetic domains. Importantly, the atomic order orientation incorporating HRTEM observation and circumferential permeability were effectively increased by the co-action of thermal activation energy and magnetic field energy during ACJA, further to enhance the magnetic properties to some extent. Based on both the numerical calculation of transient temperature rise and GMI behavior, we propose ACJA as an efficient annealing technique to achieve simultaneous best performance of [DZ/Z 0 ] max and j max for potentially magnetic sensor applications in detecting weak magnetic fields.

Comparative Study of Magnetic Properties and Microstructure for As-cast and Square-wave Pulse Current Joule Annealed Wires

“…[ at relatively low frequency is tend to enhance the resolution and accuracy of GMI sensor from sensor application perspective, so the better working frequency is chosen as 5MHz according to the sensor applied frequency ranges (5MHz~10MHz) as shown in Figure 4c. Furthermore, SPCJA (annealing at 75mA for 480s at 50Hz) annealed wire possesses an enhanced GMI property at 5MHz in comparison with the corresponding results reported by previously reference 14 Comparative Study of Magnetic Properties and Microstructure for As-cast and Square-wave Pulse Current Joule Annealed Wires achieve to 142.33%, 181.21%/Oe and 0.8Oe at 5 MHz, respectively. Significantly, the square pulse is more effective than "sin" wave annealing owing to both the high-density pulsed circumferential magnetic field and thermal activation energy in relatively long active time for increasing magnetic anisotropy and improving microstructural relaxation.…”

“…Even the time extends for a longer time, it seem to no obvious effect on GMI property as the time is up to the critical times (i.e. 480s or 600s) based on a great deal of previous experiments [11][12][13][14] .…”

Soft Magnetic Wires for Sensor Applications

“…6 (Fig. 3a, 5c, 6c) Similarly considerable progress in the optimization of melt-extracted microwires is achieved [101][102][103]: maximum GMI ratio of Co-rich melt-extracted microwires has been enhanced up to 120 % [102] and even recently up to 250 % [103]. The problem with melt-extracted microwires is that due to the fabrication process, their cross section is not perfectly circular.…”

Fabrication and Properties of Micro‐ and Nanoscale Metallic Glassy Wires: A Review

“…[102,108,109] During the fast solidification process of the methods, residual stresses were introduced which decreased magnetoimpedance performance. [108,111,112] The maximum relative change of impedance and maximum magnetic field response sensitivity of Co 68.25 Fe 4.5 Si 12.25 B 15 glass wire fabricated by Taylor method was improved from 420% and 320%/Oe in as-cast state to 600% and 95%/Oe in annealed state, respectively. [108,111,112] The maximum relative change of impedance and maximum magnetic field response sensitivity of Co 68.25 Fe 4.5 Si 12.25 B 15 glass wire fabricated by Taylor method was improved from 420% and 320%/Oe in as-cast state to 600% and 95%/Oe in annealed state, respectively.…”

“…[52,103] Therefore, various annealing techniques were introduced to decrease the residual stresses to reduce the magnetoelastic coupling and improve magnetic anisotropies, [110] and hence the magnetoimpedance performance of MG microwires was improved. [108,111,112] The maximum relative change of impedance and maximum magnetic field response sensitivity of Co 68.25 Fe 4.5 Si 12.25 B 15 glass wire fabricated by Taylor method was improved from 420% and 320%/Oe in as-cast state to 600% and 95%/Oe in annealed state, respectively. [113] Stress annealing technique can further improve magnetoimpedance performance of MG microwires by introducing magnetic anisotropy, [108,114] because it is intrinsically related to the performance.…”