Generation of second harmonic in off-diagonal magneto-impedance in Co-based amorphous ribbons

TL;DR

This study investigates the generation of second harmonic signals in off-diagonal magneto-impedance of Co-based amorphous ribbons, revealing how annealing conditions influence harmonic behavior and field dependence.

Contribution

It demonstrates the conditions under which second harmonic generation occurs in magneto-impedance and provides a quasi-static rotational model to interpret the experimental results.

Findings

Second harmonic amplitude surpasses first at high current amplitudes.

Annealing atmosphere affects harmonic field dependence behavior.

Experimental data aligns qualitatively with the rotational model.

Abstract

The off-diagonal magneto-impedance in Co-based amorphous ribbons was measured using a pick-up coil wound around the sample. The ribbons were annealed in air or in vacuum in the presence of a weak magnetic field. The evolution of the first and second harmonics in the pick-up coil voltage as a function of the current amplitude was studied. At low current amplitudes, the first harmonic dominates in the frequency spectrum of the voltage, and at sufficiently high current amplitudes, the amplitude of the second harmonic becomes higher than that of the first harmonic. For air-annealed ribbons, the asymmetric two-peak behaviour of the field dependences of the harmonic amplitudes was observed, which is related to the coupling between the amorphous phase and surface crystalline layers appearing after annealing. For vacuum-annealed samples, the first harmonic has a maximum at zero external field, and the field dependence of the second harmonic exhibits symmetric two-peak behaviour. The experimental results are interpreted in terms of a quasi-static rotational model. It is shown that the appearance of the second harmonic in the pick-up coil voltage is related to the anti-symmetrical distribution of the transverse field induced by the current. The calculated dependences are in a qualitative agreement with the experimental data.