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In order to design an energy-efficient motor, it is necessary to clarify the magnetic property of Fe-based amorphous alloys under stress. However, it is difficult to measure the magnetic property of amorphous alloys under stress because a single amorphous ribbon buckles easily under compressive stress. In this paper, we describe our measurement device equipped with a stress loading mechanism of thin ribbon and laminated bulk and compare the measurement results. Our results confirm that when the stress less than −10 MPa is applied, the deviation of maximum magnetic field’s strength at 0.5, 1, and 1.3 T increases almost linearly by compressive stress. [ABSTRACT FROM AUTHOR]

Rapid solidification process (RSP) has been widely used to fabricate Fe-based nanocrystalline alloys. To obtain amorphous structure after RSP, the number of Fe elements in the nanocrystalline alloys is limited by the amount of amorphous forming elements. Recently, strong demand for high energy efficiency electronic devices has pushed researchers to make Fe-based alloys with high magnetic flux density. However, this high Fe concentration for high magnetic flux density deteriorates the thermal stability of the amorphous structure. This means that an annealing process after RSP is critical to obtain excellent alloy magnetic properties. In this paper, to enhance the soft magnetic properties of amorphous Fe–B–Cu–C ribbons, changes in the microstructure during annealing have been investigated. [ABSTRACT FROM AUTHOR]

Amorphous Fe-P-B particles with submicron sizes were synthesized by chemical precipitation in aqueous solutions. The particles having a spherical shape exhibit good magnetic softness and high saturation magnetization. When they are precipitated in a magnetic field, they are connected to each other to form a chain shape. The high aspect ratio of the chains reduces appreciably the demagnetization field associated with isolated particles, resulting in significant improvement of high permeability performance. In this paper, investigations on the external and internal structures of the chains, uniaxial anisotropy caused by aligning the chains in an external magnetic field, frequency dispersion of permeability, and thermal change of the high permeability feature are presented. Finally, comparison of permeability for particles with various sizes is made with the present chain samples. In addition to the superior high permeability feature compared to other magnetically soft particles, the chains exhibit low loss characteristics at high frequencies up to a few GHz. It is also demonstrated that permeability is improved by annealing at 150\,\,^\circ\ C in vacuum. These results suggest that the particle chains have a high potential for high-frequency applications such as inductor cores and electromagnetic noise absorbers. [ABSTRACT FROM AUTHOR]

Magnetostrictive amorphous FeSiB and FeGaSiB thin films thickness 50 nm have been grown by the co-sputtering-evaporation technique with a range of Ar pressure (4– 8~\mu bar) to control the Ga percentage within the films and study their effect on the magnetic, structural, and magnetostriction properties. By X-ray diffraction, it was found that all the films had an amorphous structure and the only peaks were present for Si substrate. Using a magneto-optical Kerr effect magnetometer, it was found that, for the FeSiB films, the anisotropy field (H_{k} ) increased slowly as the pressure increased, while for the FeGaSiB films, the saturation field (H_{s}) \approx 4000 A/m for all pressures. For both the film sets, the coercive field (Hc) was less than 800 A/m. The magnetostriction constants (\lambda s) of the FeSiB thin films increased with increasing pressure. While for the FeGaSiB films, the magnetostriction constant decreased with increasing the sputtering gas pressure, with the maximum \lambda s = 11.4 ppm, at the lowest pressure $4~\mu $ bar. Thus, it was determined that the addition of Ga atoms reduced the intrinsic stress within the films, while maintaining the amorphous morphology. [ABSTRACT FROM AUTHOR]

This paper reports on the thermal field annealing effect of microwave permeabilities in CoFeHfO thin films. For the high resistive optimized Co[sub19] Fe[sub53] Hf[sub8] O[sub20] thin films annealed at 150° C, apart from excellent magnetic performance very low Gilbert damping constants (α < 0.017) are obtained up to film thickness of 437 nm. The results are interpreted in terms of changes in microstructure leading to structural relaxation effect and evolution of nanocrystalline Co(Fe) precipitates out of thermal field annealing. These materials with excellent low loss performance are obviously the most promising candidates for microwave device applications. [ABSTRACT FROM AUTHOR]

Entirely amorphous ribbons are successfully fabricated by adding Hf for half Cu in Fe-rich Fe86B13Cu1–xHfxand Fe85Si2B8P4Cu1–yHfyalloys, which indicates that Hf plays a positive role in promoting the glass forming ability. Differential scanning calorimetry curves of both Fe86B13Cu0.5Hf0.5and Fe85Si2B8P4Cu0.5Hf0.5amorphous ribbons show two obvious exothermic peaks, which implies the alloys will need a two-step crystallization before reaching the stable state in the subsequent crystallization process. During the normal annealing, $\alpha $ -Fe grains are formed initially at 623 K, later the Fe85Si2B8P4Cu0.5Hf0.5alloy starts to form Fe-(B, P) compounds at 723 K, while the Fe86B13Cu0.5Hf0.5alloy only begins to precipitate Fe-B compounds at a relatively higher temperature of 798 K. However, for flashing annealing, both the amorphous ribbons only start the initial crystallization of $\alpha $ -Fe phase as the annealing temperature less than $\text{T}_{x2}$ (the onset temperature of the secondary crystallization). ${\text{M}}_{s}$ (saturation magnetization) values of both Fe86B13Cu0.5Hf0.5and Fe85Si2B8P4Cu0.5Hf0.5ribbons show an increasing trend after annealing and reach a maximum of about 206.3 and 212.2 emu/g by normal annealing and 208.2 and 216.2 emu/g by flashing annealing, respectively. Therefore, crystallization phases and ${\text{M}}_{s}$ are easier and more effective to be adjusted by flash annealing, and further, the ribbons with uniform $\alpha $ -Fe phase show excellent soft magnetic properties. [ABSTRACT FROM AUTHOR]

Submicron-size amorphous particles were produced chemically from aqueous solutions. The particles in the as-made state exhibit a high saturation magnetization and magnetic softness almost equivalent to that of much larger amorphous particles produced by water atmizing. Platinum ions work effectively to control the particle size without losing magnetic softness. Magnetic softness observed for the as-made particles becomes degraded slightly by annealing. A calculation of eddy current within spheres predicts no eddy current loss even at 100 MHz for 0.3-μm particles, whereas initial permeability measurements exhibit slight indication of magnetic loss due to the broad spin resonance profile extending from 100 MHz to 10 GHz. [ABSTRACT FROM AUTHOR]

We report on the magneto-transport measurements of MgO magnetic tunnel junctions (MTJs) composed of NiFeSiB/CoFeB as the free layer for two different structures (top-type and bottom-type pinning). The magneto-transport properties of these MTJs were investigated by varying the thickness of the amorphous NiFeSiB layer for a fixed C0FeB thickness. The tunnel magnetoresistance (TMR), measured in both type of structures, exhibit the same or a higher amplitude (up to 230% measured at room temperature in the case of top-type device), comparing to the case of a single CoFeB free layer. These results suggest that hybrids free layers can be used as good candidates for MTJs with reduced saturation magnetization while keeping a high TMR ratio. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJs) with amorphous CoFeB and Co2MnSi electrodes were fabricated and examined. In the case of [Co90Fe10]100-xBx, the x = 32% boron addition reduces the magnetization by 30% compared to Co90Fe10, yet the reduction of the tunnel magnetoresistance (TMR) is over 95%. On the contrary, in the case of Co(100-x-y)MnxSiy, although net magnetization is very small at room temperature, the TMR can be as large as 7%. The character of each metalloid (boron and silicon) could be responsible for the peculiar behavior to each system. [ABSTRACT FROM AUTHOR]