Effect of magnetic field annealing on the soft magnetic properties of CoFeSiB ribbon and its fluxgate performance

Abstract

As a key part of fluxgate, the properties of magnetic core determine the performance of fluxgate sensor. We studied the effects of zero magnetic field annealing (ZFA) and longitudinal magnetic field annealing (LFA) on soft magnetic properties, magnetic anisotropy and magnetic domain structure of the Co70Fe5Si15B10 amorphous ribbon and its fluxgate sensor performance. It is found that LFA can effectively modulate the magnetic domain from irregular shape and size to wide regular strip domains. As a result, pinning effect, magnetic anisotropy and coercivity decrease, while the initial permeability increases. And finally, the sensitivity of the fluxgate become higher, and noise become less. The results show that the optimal soft magnetic properties of the ribbons are obtained after LFA at 440 °C, with the initial permeability of 21,020 and the coercivity of 0.2 A/m. We applied a square wave excitation signal of current 30 mA and frequency 2.4 kHz to test the performance of the fluxgates. It is found that the fluxgate sensitivity increases from the original 36.54 to 41.82 mV/μT after magnetic field annealing treatment, and the peak-to-peak noise (Noisep-p) value at 10 Hz bandwidth in 250 s decreases from the original 5.22 to 2.14 nT. The results show that the LFA treatment of the core has a significant effect on its magnetic properties and fluxgate performance enhancement, and these results have good implications for the construction of high-performance fluxgate.