Speaker
Description
Among plenty of examined magnetoimpedance (MI) materials researchers focus on cobalt-based alloys which are very well-known as soft magnetic materials appropriate for sensing elements [1] in cylindrical (wires) or planar (ribbons or thin films) geometries. This paper presents the results of testing the properties of the MI-element of Co$_{72.5}$Si$_{12.5}$B$_{15}$ amorphous wires, with a diameter of about 110 $\mu$m, at the beginning of the intermediate frequency range (1 MHz $\leq f \leq$ 12 MHz), positioned in a longitudinal DC external magnetic field with intensity of $H_{max}$ = 15 kA/m.
The complex MI-modulus $Z(H,f)$ exhibits a constant increase of $Z(H)$ with frequency, as well as the peak behavior observed for all frequencies, indicating the growth of the rotational magnetization contribution appearing above the domain wall relaxation frequency. These MI-profiles peaks are positioned at the anisotropy field $H_{k}$, suggesting the dominance of rotation magnetization in the circular permeability. The attained peak values of the impedance modulus of almost 100 $\Omega$ were registered at the highest frequency of 12 MHz. The $(\Delta Z/Z)_{max}$ value of 384 $\%$ was registered at a frequency of 1 MHz, while with a further increase in frequency, a constant decrease was recorded, resulting from a decrease in circular permeability.
A linear increase of the magnetic anisotropy field $H_{k}$ is observed in the frequency range $f \in$ [1 MHz, 7 MHz], that is very similar to the already observed $H_{k}(f)$ behavior of amorphous CoFeSiB wires [2]). This linear (and almost threefold enlargement) is followed by a further huge increase of $H_{k}$ in the frequency range from 8-12 MHz. The frequency dependence of the MI-ratio with the magnetic field as a parameter exhibits the maximum value of 365$\%$ ($@$ 1 MHz, 99 A/m), confirming the reliable detection of a weak magnetic field.
Acknowledgments
This research is supported in part by the Ministry of Science, Technological Development and Innovation of the Republic of Serbia and these results are parts of Grant No. 451-03-137/2025-03/200132 with the University of Kragujevac - Faculty of Technical Sciences, Čačak.
References
[1] K. Mohri, M. Yamamoto, and T. Uchiyama, “Application Topics of Amorphous Wire CMOS IC Magneto-impedance Micromagnetic Sensors for I-o-T Smart Society,” Journal of Sensors, vol. 2019, Wiley, Article 8285240, Nov. 2019. https://doi.org/10.1155/2019/8285240.
[2] J. M. Orelj, N. S. Mitrović, V. B. Pavlović, “MI-sensor Element Features and Estimation of Penetration depth and Magnetic Permeability by Magnetoresistance and Magnetoreactance of CoFeSiB Amorphous Wires”, IEEE Sensors Journal, vol. 23, no. 13. Institute of Electrical and Electronics Engineers (IEEE), pp.14017-14024, Jul. 2023, https://doi.org/10.1109/jsen.2023.3274598.
