Abstract
The giant magneto impedance, GMI, effect of Co-based metallic fibers prepared by melt-extracted technology is investigated under different bias direct electrical current Ib. The GMI curves have single peaks which are symmetric about zero field at and below 1MHz. However, the bimodal GMI curves which have asymmetric peaks are observed when Ib is over 2mA at 0.1MHz. And asymmetric GMI, AGMI, effect is also appeared at 1MHz when Ib just is 1mA and the field sensitivity of GMI effect is increased 5.6 times. The GMI effect and magnetization process is affected by the bias magnetic field profoundly induced by Ib, which is correlated with the outer shell domain structures with circumferentially magnetization easy axis existed in the outer shell of Co-rich magnetic wires with low and negative magnetostriction. Below 1 MHz, only if the bias current is over 1.5mA which induces a magnetic circumferential magnetic field is above the coercivity of 14.4A/m, the circumferential magnetization and GMI effect can experience the bias magnetic field effect. Above 1MHz, the skin effect gets stronger and significantly decreases the total participants of circular magnetization process in the fibers and consequently, the circular outer shell magnetization process gets much sensitive to circular bias magnetic field. AGMI effect with high field sensitivity is realized due to the bias current.
Highlights
The large change in the impedance of soft magnetic conductors has been referred to as the giant magneto impedance, GMI
At 0.1MHz1MHz, GMI curves gradually decrease with the increase of magnetic field intensity, and the maximum impedance value is obtained at zero magnetic field, showing a single peak GMI curve
Based on the analysis of the influence of circular magnetic field induced by bias and driving currents on GMI effect, it is found that the shell domains of Co-rich fibers are a kind of surface domains with spiral anisotropy, and the GMI curve is single peak at low frequency and double peaks at high frequency
Summary
The large change in the impedance of soft magnetic conductors has been referred to as the giant magneto impedance, GMI. The magnetization process of these metal fibers is studied theoretically and experimentally and the possible magnetic domain structure is proposed and observed[4,5,6,7,8]. Zhukova et al recently have found that the magnetization process of this kind of fibers is complex and not fully understood and mastered[9, 10] They found that due to the interplay between the shape axial and circumferential anisotropies, amorphous ferromagnetic fibers exhibit a rich variety of domainline magnetic phases[11]. Based on the study of GMI effect, this paper will investigate the magnetization process of metal fiber, explore the influence of magnetization process on electromagnetic effect, reveal possible ways to improve GMI effect, and provide reference and support for the rapid development of GMI sensors
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