Nonlinear magnetization reversal of Co-based amorphous microwires induced by an ac current

Abstract

The magnetization reversal of ferromagnetic Co-based amorphous microwires carrying ac current is studied. The frequency spectra of the voltage Vφ induced in the pick-up coil wound around the microwires were analysed and were found to depend on the ac current amplitude I0 and external longitudinal dc magnetic field He. The even harmonics are shown to dominate in the frequency spectra of Vφ if the ac current amplitude exceeds some threshold value, which strongly depends on He. A high sensitivity of the even harmonic amplitudes to the longitudinal dc field is demonstrated. The experimental data are described in terms of the Faraday law and the quasi-static Stoner-Wohlfarth model. The results obtained may be of importance for the design of weak magnetic field sensors.

Magnetization reversal process and nonlinear magneto-impedance in Cu/NiFe and Nb/NiFe composite wires

“…At higher AC current amplitudes the magnetization reversal of the sample takes place. This process is accompanied by the appearance of a nonlinear voltage response at the sample ends and in the pick-up coil wound around the sample [1,7,8]. Due to the strong magnetic field dependence, this nonlinear magneto-impedance effect is also promising for possible technological applications.…”

“…For the pick-up coil voltage V we have [8] . This sensitivity is sufficiently high and may be enhanced by increasing of the current frequency and amplitude or using the wires having more thick ferromagnetic shell and lower anisotropy field.…”

Measurement of magnetic noise in magnetoimpedance sensing element

“…At relatively high amplitudes of the excitation current, the generation of higher harmonics in voltage has been reported (the so-called nonlinear MI) [6][7][8][9][10][11][12]. The origin of the nonlinear voltage response is ascribed to the magnetization reversal of a conductor under the magnetic field generated by the current.…”

“…The noise in the sensing element was measured by using well-known method of the transferring of low-frequency range to the high-frequency range based on the principle of the heterodyne transformation. In contrast to the previous studies, we investigated the nonlinear off-diagonal MI [12], and the second harmonic amplitude in the pickup coil voltage was used for the analysis of the magnetic noise performance. The magnetic noise in the sensitive element was analyzed as a function of the excitation current amplitude.…”

Orthogonal Fluxgates

“…Thanks to this, the principle of the orthogonal fluxgate has been rediscovered. For example, an orthogonal fluxgate sensor based on a glass covered Cobased alloy with a very narrow diameter was proposed in (Antonov et al, 2001) and a similar sensor with a Permalloy/copper wire was used as the core with a 20 µm diameter (Li et al, 2004).…”