Nonlinear Magnetoimpedance Research Articles

Bias Current Effect on Second Harmonic in Asymmetric Magnetoimpedance Response in Amorphous Microwires

The influence of bias current on the second harmonic in the nonlinear magnetoimpedance in an amorphous microwire with a helical anisotropy is studied theoretically. The voltage response of the microwire is found in the framework of a rotational model. It is shown that the application of the bias current leads to the asymmetry in the field dependence of second harmonic. The second harmonic amplitude is analyzed as a function of the external field, current amplitude and the value of the bias current. The conditions of maximum field sensitivity of the second harmonic are found.

Amplification of even Harmonics in Nonlinear Magnetoimpedance Response of Amorphous Wires in Presence of Longitudinal Alternating Magnetic Field

A model to describe the influence of longitudinal alternating magnetic field on the nonli-near magnetoimpedance in amorphous wires is proposed. The appearance of even harmonics in the voltage response is shown to arise from the asymmetry in the magnetization reversal process in the wire due to the presence of the longitudinal alternating field. The behavior of even harmonics is analyzed as a function of the external field, alternating field amplitude and current amplitude.

A model for torsion-stress effect on nonlinear magnetoimpedance in amorphous wires with negative magnetostriction

A model to describe the influence of torsional stress on nonlinear magnetoimpedance in amorphous wires with negative magnetostriction is proposed. The nonlinear voltage response is found in the framework of the low-frequency approximation taking into account the spatial distribution of the circular magnetic field and the magnetoelastic anisotropy induced by the torsional stress. It is demonstrated that the application of torsional stress results in an increase of the second harmonic amplitude in voltage due to a reinforcement of helical anisotropy in the wire. The second harmonic amplitude is analyzed as a function of external field, torsional stress and current amplitude. The ranges of torsional stress and current amplitude to achieve maximal field sensitivity of the second harmonic are found.

Nonlinear Magnetoimpedance in Field- and Stress-Annealed Amorphous Ribbons

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The diagonal and off-diagonal nonlinear magnetoimpedance in amorphous ribbons with well defined magnetic anisotropy is investigated. Field- and stress-annealing are used to produce easy-ribbon-axis and hard-ribbon-axis anisotropy, respectively. The dependence of the first three harmonic components of impedance on applied magnetic field and dc bias current is discussed. The symmetry properties of diagonal and off-diagonal impedance components as functions of applied magnetic field and dc bias current are substantially different. While all the components of diagonal impedance are mainly symmetric functions of field, the off-diagonal impedance is mainly antisymmetric. It is found that the odd harmonics of diagonal impedance can be related to the second harmonic of the off-diagonal impedance and vice versa. A theoretical explanation of the observed behavior, based on the symmetry properties of nonlinear Landau–Lifshitz–Gilbert equation, is proposed. </para>

Nonlinear giant magnetoimpedance and the asymmetric circumferential magnetizationprocess in soft magnetic wires

The magnetoimpedance effect and its nonlinear terms are analysed for a(Co0.94Fe0.06)72.5Si12.5B15 amorphous wire. In order to enhance the nonlinear contribution the sample was previouslysubjected to current annealing (Joule heating) to induce a circumferential anisotropy. Theeffect of the application of a torsional strain on the nonlinear magnetoimpedance isanalysed in terms of the torsional dependence of the magnetic permeability, evaluatedthrough experimental circumferential hysteresis loops. The results obtained clearly confirmthe direct correlation between the asymmetric circumferential magnetization process andthe occurrence of nonlinear second-harmonic terms in the magnetoimpedance voltage.

Frequency spectrum of the nonlinear magnetoimpedance of multilayer film structures

Magnetization reversal by high-frequency current in FeCuNbSiB/Al/FeCuNbSiB three-layer film structures is studied. The frequency spectrum of the voltage arising in a coil wound on the sample as a function of a permanent magnetic field (nonlinear magnetoimpedance) is taken. It is shown that the frequency spectra of the voltage are qualitatively different for the longitudinal and transverse orientations of the field with respect to the direction of the current. Frequency spectrum harmonics are demonstrated to be highly sensitive to a magnetic field. A simple electrodynamic model to describe experimental data is suggested.

Nonlinear magnetoimpedance effect in soft magnetic amorphous wires extracted from melt

The nonlinear mode of the magnetoimpedance in Co-based amorphous wires extracted from the melt is studied. The frequency spectrum of a voltage induced in a pick-up coil wound around the wire is analyzed as a function of an ac current amplitude and a longitudinal dc magnetic field. It is observed that at sufficiently high ac current amplitudes even harmonics dominate in the pick-up voltage spectrum. A high sensitivity of even harmonics to the dc magnetic field is demonstrated. The studied nonlinear magnetoimpedance is promising for the design of weak magnetic field sensors.

Advantages of nonlinear giant magnetoimpedance for sensor applications

Abstract Extremely high, nonlinear magnetoimpedance (MI) effect, up to 1200% at a frequency of 4 MHz, was found and studied in an Fe 20 Ni 64 Co 16 /Cu 97 Be 3 electroplated wire. The measurements were performed in a high quality system that allows to measure simultaneously the amplitude of the most significant harmonics generated by the sample.

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

The magnetization reversal of Cu/NiFe and Nb/NiFe composite wires carrying AC current is studied. The frequency spectrum of a voltage induced in a pick-up coil wound around the wire is analyzed. The frequency spectrum is shown to consist of even harmonics within a wide range of AC current amplitudes and longitudinal DC magnetic fields. The strong dependencies of the harmonic amplitudes on the DC field are found. The results obtained may be of importance for the design of weak magnetic field sensors.