Stability Of Soft Magnetic Properties Research Articles

Ultra-fine microstructure and exceptional low coercivity developed in a high-Bs Fe-Si-B-P alloy by co-alloying Ni, Mo, and Cu

Designing soft magnetic alloys with high saturation magnetic induction (Bs) is of great importance for improving the power density of electric and electronic devices. For high-Bs nanocrystalline alloys, the main problem is the grain coarsening effect induced by high Fe content (>80 at.%), which deteriorates the soft magnetic properties. In present work, we designed new Fe-based nanocrystalline alloys by microalloying a Fe-Si-B-P alloy. The co-alloying of Ni, Mo, and Cu effectively refines the microstructure of nanocrystalline alloys from 28.5 nm to 13.1 nm and increased the stability of soft magnetic properties. Even though there are 28-nm-large surface crystallites in the amorphous precursors, an exceptional low coercivity of 1–2 A/m with a high Bs of 1.81 T was developed after nanocrystallization. These excellent magnetic properties could be maintained within a wide annealing temperature window of 50 K and an annealing time window up to 600 s for high heating rate annealing.

Extremely high Bs (Fe1-xCox)86Ni1B13 amorphous soft magnetic alloys with good bending ductility

The effects of Co content on the thermal stability, soft-magnetic properties, corrosion resistance and mechanical properties of (Fe1-xCox)86Ni1B13 (x = 0–0.25) amorphous alloys were systematically investigated. Adequate Co addition can significantly increase saturation magnetic flux density (Bs). Extremely high Bs of 1.78–1.92 T was obtained when Co content was added in the range of x = 0.05–0.25. Besides, the Curie temperature (Tc) increases markedly with the introduction of Co, exhibiting the high thermal stability of soft magnetic properties. Compared with x = 0 (Co-free) alloys, the Tc of x = 0.1 (0.1Co) alloy increases more than 100 K, far exceeding the first crystallization temperature. There is also an obvious increase in temperature intervals between the two exothermic peaks of crystallization with Co content, implying high thermal stability of the Co-containing alloys. In addition, the corrosion resistance of 0.1Co alloy was also improved compared with the Co-free alloy. Among the (Fe1-xCox)86Ni1B13 amorphous alloys, the one with 0.1Co simultaneously exhibits high Bs of 1.87 T and low Hc of 10 A/m, as well as good bending ductility at annealed state. Moreover, the underlying mechanisms of the good ductility of the 0.1Co alloy annealed under the optimal condition was also discussed from the perspective of atom bonding nature. The combination of extremely high Bs and low Hc in conjunction with good manufacturability makes the (Fe0.9Co0.1)86Ni1B13 alloys promising soft-magnetic materials for potential applications.

Optimization of crystallization behavior and soft magnetic properties of the Si-free Fe-B-P-C-Cu nanocrystalline alloys by Cu content tuning

The effect of Cu content on amorphous forming ability (AFA), crystallization behavior and soft magnetic properties of the new Si-free Fe84-xB9P3C4Cux (x = 0.7, 0.9, 1.1, 1.3 and 1.5) alloys were systematically investigated. The phase structure identified by XRD reveals that the alloys for Cu content less than 1.3 at. % have good AFA. The dependence of activation energies of nucleation and growth on Cu content shows that the growth of α-Fe grains is more difficult than the nucleation for the alloy ribbons with Cu ≤ 1.1 at. %, which is beneficial to obtain finer nanocrystalline α-Fe grains during crystallization annealing, while for those with Cu > 1.1 at. %, the growth of α-Fe grains is easier than the nucleation. The relationship between coercivity (Hc) and the annealing temperature (Ta) indicates that appropriate Cu content is beneficial to improve the stability of soft magnetic properties, especially, when annealed near the temperature of the first crystallization peak. The nanocrystalline Fe82.9B9P3C4Cu1.1 alloy exhibits a high saturation magnetic flux density of 1.84 T ~ 1.85 T and a low Hc of 13.0 A/m ~ 8.9 A/m annealed in the range of 703 K ~ 763 K.

Soft magnetic Fe-Co-based amorphous alloys with extremely high saturation magnetization exceeding 1.9 T and low coercivity of 2 A/m

Extremely high saturated magnetization (Bs) of 1.92 T in conjunction with low coercivity (Hc) of 2 A/m was found to be achieved for (Fe0.8Co0.2)85B14Si1 amorphous alloy. The high Bs above 1.9 T was the first evidence for amorphous alloys. The slight increase of B to 15%B reduces Bs to 1.88 T. The high Bs of 1.92 T is much higher than that (1.63 T) for the new commercial Fe-B-Si-C amorphous alloy and comparable to commercial Fe-Si steels. The excellent soft magnetic properties, which cannot be obtained for all soft magnetic alloys including amorphous, nanocrystalline and crystalline alloys reported to date, were obtained by annealing the as-spun amorphous alloy ribbon for 600 s at 593 K in a magnetic field of 15.9 kA/m. The high Bs above 1.9 T was obtained in a rather wide annealing conditions of 543–603 K and 300–1200 s, indicating the ease of achieving the excellent soft magnetic properties. No appreciable crystalline phase is recognized in the annealed ribbon even by HRTEM and electron diffraction pattern. The effective permeability at 1 kHz also exhibits high values above 20000 and the Curie temperature also shows high values above the onset temperature of crystallization corresponding to high thermal stability of soft magnetic properties. Besides, the (Fe0.8Co0.2)84B15Si1 and (Fe0.8Co0.2)85B14Si1 amorphous alloys exhibit good bending ductility even in the optimal annealed state. The corrosion resistance in 3.5 mass% NaCl aqueous solution is better than that for the commercial Fe-Si-B-C amorphous alloy. The first synthesis of the Fe-based amorphous alloy having simultaneously high Bs above 1.9 T, low Hc of about 2 A/m, high effective permeability, high Tc and good bending ductility is promising for future extension of amorphous alloys as engineering soft magnetic materials.

Long-term stability of soft magnetic properties of amorphous and nanocrystalline alloys based on iron

In the present paper long-term stability of magnetic properties of different amorphous and nanocrystalline alloys was studied. Magnetic properties were measured for annealed samples (300<Ta<900 K) directly after annealing and after long-term aging at room temperature. It was shown that for the Fe 75.3Cu 1Zr 1.7Si 13B 9 alloy magnetic permeability of the optimized samples is stable during 8 years aging. For Fe 86− x Nb x B 14 alloys the observed long-term instability (3 years aging) is due to annealing out of free volume leading to formations of small iron clusters coherent with the amorphous surroundings.

Field induced anisotropy and stability of soft magnetic properties towards high temperature in Co-rich nanocrystalline FeCoNbB alloys

We report on a beneficial effect of the external magnetic field applied during the heat treatment on the soft magnetic characteristics of the ( Fe 1 - x Co x ) 81 Nb 7 B 12 ( x = 0.5 , 0.75 and 1) alloys. The effect of field-annealing is more significant in ( Fe 0.5 Co 0.5 ) 81 Nb 7 B 12 where the transverse field induced anisotropies up to K u ∼ 1350 J / m 3 have been observed. Sheared loops with a good field linearity up to H k ∼ 2000 A / m were achieved for all transverse field-annealed samples. Such characteristics are of particular interest mostly for the high frequency and sensors applications. The stability of the soft magnetic properties towards the high temperatures was improved with an increase of cobalt content.

Thermal Stability of Soft Magnetic Properties in Fe/CoZr Multilayer Films

The thermal stability of the structural and soft magnetic properties of sputter-deposited Fe/Co 92 Zr 8 multilayer films was investigated. The thermal stability of the film coercivity is improved by using very thin bilayers. The good thermal stability is attributed to the suppression of grain growth in the film plane. When the Fe layers are made thinner than 10 nm, a low coercivity of less than 2 Oe can be obtained even after annealing at 600°C, and an effective permeability of about 2000 can be obtained after annealing at 500°C.

Thermal Stability of Fe-Zr/Fe-Zr-N Soft Magnetic Multilayered Films

stract-Fe-Zr/Fe-Zr-N multilayered films were prepared by alternation of Fe-Zr sputtering and electron cyclotron resonance (ECR) plasma nitridation. Thermal stability of the films' soft magnetic properties was investigated. A saturation flux density of B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> =1.8 T, coercivity H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> =88 A/m and relative permeability μ'≫3000 (at 20 MHz) were obtained for Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">92</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> /Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">92</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> -N multilayered film after annealing at 773K for 3600 s. Addition of Zr to Fe/Fe-N multilayered films effectively improves the thermal stability of soft magnetic properties.

Magnetic properties of Fe-Ta-(b)-N films

The in-plane magnetic anisotropy and thickness dependence of soft magnetic properties for Fe-Ta-N films near the eutectic composition, annealed either in a rotating magnetic field, in a static field, or with no magnetic field, were investigated in detail. The soft magnetic films were prepared by RF reactive sputtering. The films with thicknesses greater than around 2 mu m have good soft magnetic properties. For those with thicknesses less than around 1 mu m, the soft magnetic properties deteriorate and the domain structure changes with decreasing thickness. The films annealed without magnetic field or in a rotating field have an isotropic high permeability ( mu '>or=5000 at 1 MHz) and a low anisotropy field (H/sub k/ approximately=50 A/m), whereas for the films annealed in a static field, uniaxial anisotropy is induced. This anisotropy increases with increasing N concentration. Moreover, B was added to the Fe-Ta-N system, and the relation between the structures and soft magnetic properties of Fe-Ta-B-N films was investigated. By adding B to Fe-Ta-N system, the thermal stability of soft magnetic properties is improved.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

ＥＣＲプラズマ窒化によるＦｅ‐Ｚｒ／Ｆｅ‐Ｚｒ‐Ｎ軟磁性多層膜の耐熱性

Fe-Zr/Fe-Zr-N multilayered films were prepared by alternation of Fe-Zr sputtering and electron cyclotron resonance (ECR) plasma nitridation, and the thermal stability of their soft magnetic properties were inverstigated. Saturation flux density Bs = 1.8 T, coercivity Hc = 88 A/m and relative permeability μ' > 3000 (at 20 MHz) were respectively obtained on Fe92Zr8/Fe92Zr8-N multilayered film after annealing at 773 K for 3600 s. Addition of Zr for Fe/Fe-N multilayered films improved effectively the thermai stability of soft magnetic properties.

Correlation between thermal stability of soft magnetic properties and structural relaxation in Co58Fe5Ni10Si11B16 metallic glass

Effects of isochronal and isothermal annealings on permeability, coercive field, field-induced anisotropy and electrical resistivity in Co58Fe5Ni10Si11B16 metallic glass pre-annealed at 743 K for 60 min were examined to clarify the correlation between thermal stability of soft magnetic properties and structural relaxation. It was found that both soft magnetic properties and electrical resistivity changed reversibly, depending on annealing temperature, and the values of activation energy for the changes in these properties were very close, lying in the range 1.8 and 2.0 eV. However, although the deterioration of soft magnetic properties was observed in the specimens annealed below the Curie temperature (Tc), the resistivity changes occurred significantly even in the specimens above (Tc), The results strongly suggest that the changes in soft magnetic properties are attributed to an anisotropic chemical short-range ordering (CSRO) among the cobalt, iron and nickel atoms, and the resistivity changes (structural relaxation) are mainly due to an isotropic CSRO.

Thermal stability of softmagnetic properties of Co-(Nb,Ta)-(Zr, Hf) films with high saturation magnetization

Thermal stability of softmagnetic properties of amorphous Co-(Nb,Ta) - (Zr,Hf) systems with high saturation magnetization (4πM s ) was studied. It was found that Hf-containing films, especially Co 88 Ta 8 Hf 4 alloy, with high 4πM s (∼ 10000 Gauss) as high as that of Sendust alloy were thermally very stable even up to 500°C, while the conventional Co-based amorphous films with the same 4πM s could not tolerate such high temperature annealing because of crystallization. The relation between the structural changes and the magnetic properties of Co 83 (Nb,Ta) 13 Zr 4 film (with 4πM s ∼8500 Gauss) was also investigated. These films have promising properties as magnetic head core materials for high performance VTR since they can cope with high coercivity media and withstand high temperature fabrication processes.

Annealing effects and short-range ordering in the non-magnetostrictive amorphous alloy Co58Ni10Fe5Si11B16

Effects of isothermal and isochronal annealing on the coercive field and the effective magnetic anisotropy in the as-quenched and the stress relieved amorphous alloy Co58Ni10Fe5Si11B16 were investigated. The mechanisms of the deterioration of soft magnetic properties in non-magnetostrictive amorphous alloys by annealing at low temperatures,T a <T c , are discussed. It turned out, that short-range ordering, i.e., topological short-range ordering (TSRO) and chemical short-range ordering (CSRO), caused by annealing lead to changes of the magnetostrictionλ s , and of the induced magnetic anisotropyK i . Both effects give rise to an increase of the coercive field. In addition, the kinetics of short-range ordering was studied and from these data, which are closely related to the stability of soft magnetic properties, the activation energy and a preexponential factor was derived:Q s.r=0.7eV,v 0=9.6×103s−1.