The GMI effect in nanocrystalline FeCuNbSiB multilayered films with a SiO₂outer layer

Abstract

The giant magneto-impedance (GMI) effect in nanocrystalline FeCuNbSiB multilayered films was investigated. The multilayered films were deposited by magnetron sputter equipment with an additional SiO2 outer layer. The GMI ratio of multilayered films varied with the annealing temperature due to the changing orientation of the magnetic moments. The maximum GMI frequency of the nanocrystalline state was lower than that of the amorphous state, decreasing from 12.3 to 5.45 MHz. Ageing experiments were carried out for films with and without the insulator layer. It was seen that the GMI ratio of the multilayer film with a covered SiO2 layer was preserved well even after ageing.

Shape Anisotropy in Magneto-Impedance NiFe-Based Microsensors

“…4 This structure involves a conductive track between two ferromagnetic layers. Fe-based amorphous or nanocrystalline ferromagnetic materials, [5][6][7][8][9][10] particularly NiFe, 4,[11][12][13][14] have been studied leading to magneto-impedance up to 400% at excitation frequencies in a range of several tens to several hundreds of MHz. However, these high frequencies, linked to under-μm thicknesses, make difficult the integration of an associated electronics.…”

Giant magnetoimpedance effect of multilayered structure (F/SiO2)3/Ag/(SiO2/F)3 films deposited in a longitudinal magnetic field

“…In our experiments, the longitudinal magnetic field applied during deposition process may induce ordering distribution of atomic magnetic moments in the film plane, and this helps to form the longitudinal domain structure. Therefore, the permeability parallel to the film's plane will be enhanced due to disappearance of the perpendicular anisotropy [10]. Magnetoimpedance (MI) measurements show that the GMI effect almost cannot be detected in the non-field-deposited samples, because the soft magnetic property in the non-field-deposited samples is poor.…”

“…The SiO 2 layers play an important role in multilayered films. The SiO 2 insulator layers may prevent the atomic diffusion between the magnetic layers and conductive layer, and the conductive contribution of the conductive layer is increased, while the AC magnetic field can still cross the insulator layers [10]. In addition, the SiO 2 layers decrease the eddy current losses obviously within the ferromagnetic films, especially at higher frequencies, and the effective permeability is increased.…”

“…The GMI effect is mainly related to the changes in skin effect and permeability with magnetic field [2]. In recent years, the investigations on the GMI effect have been extended from uniform magnetic alloy, such as wires, ribbons and films, to composite structures consisting of magnetic materials and non-magnetic materials, such as composite wires [5,6], sandwiched ribbons [7,8] and multilayered films [9][10][11]. Wires and ribbons should be welded and straightened in the installation process of magnetic sensors, so their extensive applications in the magnetic micro-sensors are restricted.…”

Enhanced magnetoimpedance effect of carbon fiber/Fe-based alloy coaxial composite by tensile stress

“…The composite of carbon fiber and FeNi with the smaller diameter and the higher elastic coefficient displays a large GMI result at a relative small applied field than traditional metal coaxial structures, which provides a kind of competitive material for future magnetic sensor. In contrast, because the symmetry of wires [32][33][34][35][36] is better than ribbons [37,38], films [39][40][41] and other stratified [42] structures, the GMI ratio of the former is better the latter. Although Co-based amorphous wires and composite wires [27,32,33] have higher GMI ratio even at larger magnetic field, cobalt is an expensive metal, which will restrict the extension in commercial application.…”