Giant magnetoimpedance effect in a positive magnetostrictive glass-coated amorphous microwire

Abstract

The giant magnetoimpedance ͑GMI͒ effect in positive magnetostrictive glass-coated amorphous Co 83.2 Mn 7.6 Si 5.8 B 3.3 microwire has been studied as a function of a dc magnetic field Ϫ140ϽH dc Ͻ140 Oe and frequency 0.1Ͻ f Ͻ12.85 MHz. A maximum change of 43% in the MI of the as-quenched sample has been observed around 5 MHz frequency. Heat treatment of the sample by passing a dc current of 50 mA through it enhances the MI value to a large extent ͑maximum change ϳ94%͒ by increasing the outer domain volume and inducing a transverse anisotropy. On the other hand, application of an external tensile stress reduces the GMI value by increasing the inner core domain and developing an axial anisotropy. In an as-quenched sample, the maximum value of MI is observed at H dc ϳ0 when measured at frequency f Ͻ8 MHz beyond which a two peak MI profile is seen. The heat-treated sample shows this two peak behavior from a much lower frequency ͑below 1 MHz͒ and additional peaks at H dc ϳ0 for f Ͼ10 MHz. Asymmetry in the MI peaks of a microwire has been produced by passing a dc current through the sample during impedance measurement. The magnetization of the as-quenched and heat-treated samples has also been studied to understand the domain structure and magnetoimpedance results.

Advanced Magnetic Microwires as Sensing Elements for LC-Resonant-Type Magnetoimpedance Sensors: A Comprehensive Review

“…7 The magnetic-field dependences of magnetoimpedance GMI(%) for sample no. 1 measured at different frequencies the ferromagnetic resonance in the high-frequency range of 1-10 GHz, for typical Co-based microwires [27,28]. In the present work, it should be noted that the appearance of a multiple-peak GMI behavior is not a common feature of the frequency dependence of the GMI.…”

“…In addition, the GMI sensors have been found to be more field sensitive than the existing giant magneto-resistance (GMR) sensors [23,24]. The GMR materials generally involve large fields to obtain a response of a few percent, whereas the GMI materials can produce a few hundred percent changes in the impedance at very small magnetic fields [25][26][27][28][29][30]. For instance, a GMR sensor has a maximum sensitivity of ∼10-20%/Oe, while the field sensitivity of a GMI sensor can reach an extremely high value of 500%/Oe [31].…”

Stripe-to-bubble transition of magnetic domains at the spin reorientation of (Fe/Ni)/Cu/Ni/Cu(001)

“…8, 19 Then since 20 ML Ni on Cu(001) has a perpendicular magnetization, 20 the SRT of the (Fe/Ni) layer in the [Fe/ Ni(5 ML)]/Cu/Ni(20 ML) system is equivalent to the SRT of a (Fe/Ni) film within a perpendicular magnetic field whose stiength varies with the interlayer Cu thickness. At the PEEM beamline, prior to the PEEM measurement, the sample was magnetized in a 1 kOe magnetic field normal to the film surface to wipe out the magnetic domains of the 20 ML Ni film, ensuring a uniform exchange coupling between the Ni and the (Fe/Ni) films.…”

Giant magnetoimpedance effect in a glass-coated microwire LC-resonator for high-frequency sensitive magnetic sensor applications

“…A large increase of the circumferential permeability can be achieved by applying an ac current of the frequency sufficiently high to excite the resonance of the sample. This large circumferential permeability at the resonance strongly decreases the penetration depth and, therefore increases the impedance of the sample [13,14]. In this context, Co-based amorphous wires are good candidates for GMI sensor applications, because they possess extremely high circumferential permeability arising from their circumferential domain structure [15][16][17][18].…”

“…It originates from the skin effect as a consequence of the change in the permeability of a magnetic material under the influence of an external dc magnetic field applied along the magnetic conductor [11]. When the frequency of ac current flowing through the sample is high enough, the skin effect plays an important role, reducing the effective section of the sample and so leading to a noticeable GMI effect [10][11][12][13][14].…”