Frequency Analysis of the GMI Effect in a ThinFilm Magnetic Structure With an Insulator in the Linear and Nonlinear Operating Regimes

In this work, we propose a micromagnetic approach to model the CoFeSiB-SiO2-Al-SiO2-CoFeSiB structure, which exhibits the giant magnetoimpedance effect. It was found that in the nonlinear mode of detecting an external magnetic field of about 1 Oe (at a current I = 37 mA), directed along the magnetic anisotropy axis of the CoFeSiB film, the signal increases almost 3 times when the frequency changes from 10 to 40 MHz (from about 90.9 to 268.9 mV). At the same time, the variation of the current amplitude from 12.3 to 37 mA at a frequency of 20 MHz leads to an increase in the signal amplitude by several orders of magnitude (from 3.8 to 146 mV). In this case, the resonant response (∼146 mV) at a relatively low magnetic field (H≈1 Oe) is observed due to the predominance of higher harmonics, while in the linear mode (I<37 mA) this field becomes insufficient to achieve the maximum output signal. The results obtained can be used to develop a promising type of giant magnetoimpedance sensors based on thin-film magnetic structure with an insulating layer separating the current-carrying conductor from the ferromagnetic layer to reduce the eddy current loss at high frequencies.