The Mumetal thin film is a good candidate for the giant magnetoimpedance (GMI) sensor because of its ultra magnetic softness. In this study, we investigated the magnetic softness of the mumetal thin films by measuring the incremental permeability in transverse direction to the external magnetic field and the MI effect at various frequencies with various driving currents.
A thorough study about the influences of Mn substitution for Fe on the microstructure and magnetic characteristics of $Fe_{73.5-x}Mn-{x}Si_{13.5}B_{9}Nb_{3}Cu_1$ (x = 1, 3, 5) alloys prepared by the melt-spinning technique has been performed. Nanocomposites composed of nanoscale $(Fe,Mn)_{3}Si$ magnetic phase embedded in an amorphous matrix were obtained by annealing their amorphous alloys at $535^{\circ}C$ for 1 hour. The addition of Mn causes a slight increase in the mean grain size. The Curie temperatures of the initial amorphous phase and of the nanocrystals phase decreased, while the Curie temperature of the remaining amorphous phase remained nearly constant with increasing Mn content. Soft magnetic properties of the crystallized samples have been significantly improved by a proper thermal treatment. Accordingly, the giant magnetoimpedance effect is observed and ascribed to the increase of the magnetic permeability, and the decrease of the coercivity of the samples. The increased magnetic permeability is resulted from a decrease in the magnetocrystalline anisotropy and saturation magnetostriction.
The dependence of the magnetoimpedance effect (MI) on magnetic properties has been investigated in mumetal thin films prepared by rf magnetron sputtering. Coercivity of thin films prepared at 400 W was about 0.4 Oe, and the magnetic anisotropy field of films deposited under a uniaxial magnetic field decreased with increasing film thickness. The saturation magnetization of mumetal films increased with rising input power and thickness, and was smaller than that of permalloy films. Transverse incremental Permeability (TPR) of films of 1 ㎛ thick increased with increasing effective permeability. The magneto impedance ratio (MIR) was proportional to TPR in films 1 ㎛ thick but in spite of lower effective permeability at higher thicknesses, MIR increased due to skin effect. The height of the double peaks in the MIR curves decreased with decreasing anisotropy and thickness. The maximum MIR value for a 4 ㎛ thick 75 % at 36.5 ㎒.
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