Papers by Keyword: Soft Magnetic Properties

Abstract: In this study, we demonstrate the synthesis of an Fe₇₈Si₉B₁₀P₃ amorphous alloy by three pathways: mechanical alloying, melt-spinning and a combination of melt-spinning and ball milling. Microstructure, thermal stability and soft magnetic properties of the melt-spun and mechanically alloyed powders are comparatively studied. Ball milling of previously melt-spun samples led to an amorphous powder with an average particle size of ~2.4 μm after 20 hrs of milling. Mechanical alloying of elemental Fe-Si-B-P powders in a planetary ball mill for up to 100 hrs led only to a partial amorphisation of powder with a median particle size of ~1.3 μm. Differential thermal analysis of the amorphous ribbon revealed that the amorphous phase was stable up to ~520 °C, at which the crystallization process occurred. The melt spun ribbons exhibited excellent soft ferromagnetic behavior, including high saturation magnetization (M_s) of ~171 emu/g and a low coercivity (H_c) of ~2.8 Oe. In the 20 hrs milled ribbons, due to a probable partial anisotropy which induced by ball milling stress, the M_s value decreased slightly to ~161 emu/g but the Hc increased to ~38 Oe. The mechanically alloyed samples present a relatively lower M_s of ~154 emu/g and higher H_c of ~43 Oe. It is to be noted that the milling of ribbons is usually inevitable due to their technological restrictions in use.

Abstract: Iron-based amorphous alloys have attracted technological and scientific interests due to their excellent soft magnetic properties. In the present study, Ni_0.5Zn_0.5Fe₂O₄/Fe₇₆Si₉B₁₀P₅ soft magnetic composites cylinder of 15 mm diameter and 3 mm thickness was prepared by spark plasma sintering at the temperature of 780 K. The amorphous Fe-based soft magnetic composites Ni_0.5Zn_0.5Fe₂O₄/Fe₇₆Si₉B₁₀P₅ exhibited good magnetic properties after annealing treatment at temperature ranging from 643 K to 743 K. The beneficial effects of treatment under different temperatures were discussed in terms of the improved magnetic performance of Ni_0.5Zn_0.5Fe₂O₄/Fe₇₆Si₉B₁₀P₅ soft magnetic composites.

Abstract: [(Fe_0.5Co_0.5)_0.75B_0.2Si_0.05]₉₆Nb₄}_100-x,y(Gd_x, Cu_y) (x = 0.5, 1 and 2), (y = 0.5) alloys with different diameters were prepared by copper mold casting. The structure, the thermal and the magnetic properties were studied by X-ray diffraction, differential scanning calorimetry and vibrating sample magnetometry, respectively. Minor Cu addition completely changes the crystallization behavior, and also the glass-forming ability decreases because of the decrease in the supercooled liquid region. However, the magnetic properties are significantly improved upon annealing because of the precipitation of (Fe,Co) phase. In case of [(Fe_0.5Co_0.5)_0.75B_0.2Si_0.05]₉₆Nb₄}_100-x (Gd_x) glass, Gd addition does not change the crystallization behavior. In turn, it increases the supercooled liquid region when compared with [(Fe_0.5Co_0.5)_0.75B_0.2Si_0.05]₉₆Nb_4, but even then the glass-forming ability is reduced (critical glassy diameter d_c < 1.5 mm). The saturation magnetization of the glass is also decreased with increasing Gd content.

Abstract: After the medium-frequency magnetic pulse treating (frequency 1500-2000Hz, field intensity 200-250Oe) on amorphous Fe (Co)-M-B-Cu alloys, the vacuum anealing at low-temperature were in progress at 50°C-100°C for 30 min and 60 min. The soft magnetic properties of nanocrystalline alloy obtained by above mentioned treatments were measured by the vibrational specimen magnetometer. The results show that the structral relaxation , free volume migration and annihilation during the vacuum annealing will lead to the reduction of like-vacancy defects concentration and distortion stress. So the soft magnetic properties of nanocrystalline alloy will be improved further.

Abstract: The [Fe-Co-Si (2 nm)/native oxide]_N multilayer films weredeposited on glass substrate by DC magnetron sputtering. The effect of repetitionnumber N on static and dynamicmagnetic properties of the multilayer films was investigated. Good soft magnetic properties have been obtained inthe multilayer films with repetition number more than 30. Relatively highvalues of the complex permeability and ferromagnetic resonance frequency wereobtained and they can be adjusted by changing the repetition number of themultilayer films.

Abstract: Bulk Fe₇₃Nb₃Al₂Ge₂P₉C₆B₄Si₁ metallic glass with the diameter of 2 mm was prepared by copper mold casting. The Fe-based metallic glass exhibits good magnetic properties with high saturation magnetization and low saturated magnetostriction. The saturation magnetization and coercive force remains almost unchanged with annealing temperature below the crystallization temperature. The crystallization leads to the decrease in the softness of magnetic properties. The Fe-based glass exhibits a good correspondence between large glass-forming ability and good soft magnetic properties.

Abstract: Recently some nanocrystalline soft magnetic materials containing nanosized α-Fe grains have been obtained by crystallization of amorphous melt-spun ribbons. These structures are nanocomposites in which nanosized grains are distributed within an amorphous matrix. The soft magnetic ribbons composed of Fe₈₀B₁₀Si₈Nb₁Cu₁ alloy were prepared by melt spinning method with different quenching rates (wheel speed of 10, 20 and 40 m/s). The XRD results exhibit an increase in the copper wheel speed (quenching rate) causes the fraction of crystallinity and grain size to decrease. The grain size varies in the range of 20 to 200 nm that is in good agreement with TEM results. The VSM results show that these nanostructured samples exhibit coercivity in the range of 10 to 30 A/m and magnetic saturation in the range of 1.5 to 1.7 T.

Abstract: The soft magnetic properties of Fe-6.5wt.%Si alloy powders produced via high pressure gas atomization under different powder sizes, environments (atmospheric and vacuum) and heat-treatment were presented by vibrating sample magnetometer (VSM), respectively. It is found that the soft magnetic properties of powder gradually grow up as the increasing of the powder size under atmospheric and vacuum environments. However, the using of vacuum environment has an optimal capacity to strengthening the properties rather than atmospheric environment. The heat-treatment of 1000°C for 2 hours offers considerable potential for improving the soft magnetic properties of the powders.

Abstract: The [Fe-Co-Si (d)/native oxid₅₀ multilayer films were deposited on Kapton substrate and glass substrate by DC magnetron sputtering. The effect of substrate on magnetic and electric properties of the multilayer films was investigated. Compared to the films on glass substrates, higher coercivity, larger uniaxial-anisotropy field were achieved for the flexible films. The values of the resistivities for the flexible films are of the order of 10 mΩcm, which is two orders higher than the value of 0.1 mΩcm for the multilayer films on glass substrates. Furthermore, higher f_r was found in the flexible films. It is believed that the [Fe-Co-Si (d)/native oxide]₅₀ multilayer films on flexible substrates can find its wide applications at high frequency for various purposes.

Abstract: The electromagnetic noise suppression characteristics of a series of FeCoBM -Al2O3 amorphous soft magnetic films were reported in the frequency range from 0.5GHz to 6 GHz. Effect of dopants on the reflection coefficient (S11), transmission coefficient (S21) and power loss (PLOSS/PIN) of as-deposited FeCoBM(M=Nb, Zr, Hf, Ta, Mo, Ti)-Al2O3 films were studied. The (Fe40Co40B20)89Mo8–(Al2O3)3 film had the highest power loss with the value of 0.85 at 6GHz. The transmission properties of the FeCoBNi-Al2O3 also studied in the paper. The power loss of the (Fe40Co40B20)68.36Ni28.64–(Al2O3)3 film was more than 0.6 from 3.0-6.0GHz, which had the best electromagnetic noise suppression characteristics. These results show that the presented films possesses potential in noise suppressor applied in electronic devices .