Excellent Soft Magnetic Characteristics Research Articles

A systematic investigations on effect of annealing temperature on magnetic properties of a promising soft magnetic Co35Cr5Fe10Ni30Ti20 HEA

The present study investigates the effect of different annealing temperatures on phase formation, microstructure, and their correlation with magnetic properties of a promising soft magnetic Co35Cr5Fe10Ni30Ti20 High Entropy Alloy (HEA) design developed by our research group previously. We reproduced the Co35Cr5Fe10Ni30Ti20 HEA through the mechanical alloying and found the mixture of fcc and R-phase having Ms = 74.8 emu/g and Hc= 12.92 Oe. The different annealing temperature was decided based on the DTA analysis of the synthesized sample. The samples were annealed at 200, 500, 700, 790, 870, and 965 ͦ C for 2 h to study the change in the phase evolution and magnetic behavior. Phase transformation was observed for 500 ͦ C annealed HEA, and the value of Ms (82.38 emu/g) and Hc (41.49 Oe) increased after annealing at 500 ͦC. Interestingly, the samples annealed at high temperatures (>700 °C) have a high value of Ms and a significantly low value of Hc (<2 Oe). Among annealed Co35Cr5Fe10Ni30Ti20 HEA, 790 ͦ C annealed HEA has the highest value of Ms (90.79 emu/g) and the lowest Hc (1.66 Oe)of HEAs reported so far. The concluding reason behind the high value of Msfor annealed HEAs area decrease in lattice parameter, i.e., improved magnetic interaction and a change in volume phase fraction of synthesized phases. However, the soft magnetic behavior of high-temperature annealed HEA is attributed to the synergetic effect of the decrease in magneto-crystalline anisotropy, particle size, and surface anisotropy. The value of Ms and Hc for the 790 ̊C annealed HEA is comparable to some commercial soft magnets, such as Supermalloy, Ni-Zn ferrite, and Mn-Zn ferrite. Thus, the designed and developed Co35Cr5Fe10Ni30Ti20HEA showed excellent soft magnetic characteristics even after annealing at high temperatures and may be further considered for industrial applications.

Effect of Magnetic Annealing on Magnetic Characteristic of Amorphous Wound Core

In this paper, in order to make a clear principal cause in increasing iron loss of amorphous wound cores in processing, effects of bending stress on magnetic characteristics of a Fe-based amorphous wound core are clarified. The amorphous magnetic materials have been widely used as a core material of power transformers to reduce iron loss due to their excellent soft magnetic characteristics. However, the amorphous magnetic material has an issue that the building factor (B.F.) is very large in comparison with that of grain-oriented electrical steel sheets. The amorphous transformers usually use a wound core formed by stacking plural amorphous sheets in different lengths. Bending stress is, therefore, generated at each corner of the wound core in processing. Due to this bending stress, the magnetic characteristics of the wound core deteriorate. The deterioration of magnetic characteristics of the wound amorphous core is so large because of the large magnetostriction constant. As a result, the B.F. of this material becomes larger. In order to remove the residual stress, which is generated in the wound core including the bending stress, the amorphous wound core is usually annealed in a magnetic field, which is called “a magnetic annealing.” In this paper, the effect of the magnetic annealing on the magnetic properties is studied experimentally by evaluating some wound amorphous model cores. As a result, a suitable magnetic annealing condition is clarified and the iron loss of the wound amorphous model core is reduced by 65.7%.

Enhancement of in-plane uniaxial magnetic anisotropy for patterned nanoparticle films fabricated by electric field-assisted deposition

The patterned FeNi nanoparticle films with strip width 60µm were prepared by electric field-assisted deposition technique. Application of electric field drove the accelerating deposition of the condensed nanoparticles, promoting the formation of the films with high stacking density. Besides the excellent soft magnetic characteristics, the samples showed an obvious enhancement of in-plane uniaxial magnetic anisotropy when they were annealed in vacuum environment at proper temperatures. The increase of in-plane uniaxial magnetic anisotropy, which is due to the release of stress with increasing temperature, is also confirmed by scanning microwave permeability spectra in GHz range. The experimental results imply that optimization of in-plane uniaxial magnetic anisotropy is particularly attractive for the application of electric field deposited soft magnetic nanoparticle films in the high-temperature processing electromagnetic devices.

Microwave absorption performance of magnetic Fe–Ni–P nanoparticles electrolessly plated on hollow glass microspheres

Abstract Magnetic Fe–Ni–P nanoparticles have been successfully fabricated on hollow glass microspheres via electroless plating for the application of lightweight microwave absorbers. The resultant materials were characterized by field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), X-ray diffraction analysis (XRD), vibrating sample magnetometer (VSM) and vector network analyzer. The results show that compact and uniform Fe–Ni–P nanoparticles with the average diameter of about 150 nm have been successfully plated on the hollow glass microspheres. The plated microspheres exhibit excellent soft magnetic characteristics with high saturation magnetization and low coercivity, and the soft magnetic characteristic behaves better with the increasing of iron content in the coatings. Microwave absorption performance shows the maximum reflection loss of the composite powder reaches −49.2 dB at the frequency of 7.7 GHz with the thickness of 5 mm, and the bandwidth with the reflection loss less than −20 dB exceeds 2.2 GHz.

The Migration Behavior of Atomic Clusters in Early Nanocrystalline Process of Soft Magnetic Finemet Alloy

The Finemet alloys are commonly used as cores in transformers and generators, stress and field sensors in technological application for their excellent soft magnetic characteristics. To clarify the nanocrystallization mechanism of Finemet especially about the atomic migration in early stage is very essential for developing their distinctive characteristics. In this study, we investigate the migration behavior of atoms in order to clarify the mechanism of the early-stage nanocrystallization in amorphous Finemet alloys. The Fe(73.5)Si(13.5)B9Nb3Cu1 amorphous ribbons were prepared by single-roller melt-spinning process in argon atmosphere, and then annealed at 350 degrees C-400 degrees C for 10 minutes in vacuum. The atom force microscope (AFM) and the coincidence Doppler broadening spectra (CDB) were used to characterize the migration behavior of different atoms in Fe(73.5)Si(13.5)B9Nb3Cu1 amorphous alloy during the early-stage nanocrystallization. The X-ray diffraction (XRD) patterns show that all annealed samples are in the amorphous state. But the AFM observation shows clearly that there are many small atomic clusters (nuclei) which distribute in the amorphous matrix of the annealed samples. With increasing annealing temperature, there is a significant increase in the amount of atomic clusters and a dramatic drop in the average size of clusters with very limited Cu contention in the samples, which reflect the structural evolution into more homogeneity. The CDB spectrum indicates that the peaks of positron annihilation spectrum are gradually reduced, which means the number of grain boundary and the defects in samples are gradually increased. It can be concluded that more defects are introduced by the formation of atomic clusters through atomic migration during the early-stage nanocrystallization in Fe(73.5)Si(13.5)B9Nb3Cu1 amorphous alloys.

Magnetic anisotropy in Fe nanocrystals fabricated by GDM

Ferromagnetic nanocrystals composed of nano-sized grains show excellent soft magnetic characteristics and their mechanism is explained by a random anisotropy model(RAM). We have been studied nanocrystal systems with ferromagnetic 3d elements to understand the RAM. Fe nanocryatals were fabricated with a gas condensation and deposition method(GDM). The oxygen content in an as-deposited Fe nanocryatal was about 20 %. Hysteresis loop shifts observed in magnetic field cool measurements suggest the presence of antiferromagentic oxides. Dependence of room temperature coercive forces on the grain size(D) is not D6 but D3.4. Magnetization curves often seen in thin films with stripe domain structures were observed at room temperature irrespective to the sort of substrates. The presence of perpendicular magnetic anisotropy was suggested.

Preparation of Bulk Glassy Fe&lt;SUB&gt;76&lt;/SUB&gt;Si&lt;SUB&gt;9&lt;/SUB&gt;B&lt;SUB&gt;10&lt;/SUB&gt;P&lt;SUB&gt;5&lt;/SUB&gt; as a Soft Magnetic Material by Spark Plasma Sintering

Preparation of a soft magnetic Fe 76 Si 9 B 10 P 5 glassy bulk material has been carried out by the spark plasma sintering (SPS) technique below the glass transition temperature. The glassy powders were consolidated into bulk forms with relative densities above 98.7% through sintering them at 740 K under a pressure of 600 MPa while the samples still keep a glassy state. These as-sintered samples with a diameter of 15 mm exhibited excellent soft magnetic characteristics, which is as good as that of the cast samples with a size of 2.5 mm.

Cantilevered actuator using magnetostrictive thin film

This paper describes a cantilevered magnetic actuator driven by magnetostriction in a low magnetic field. The dimensions of the two layers actuator were 1×5 mm and amorphous FeSiB was used as the magnetostrictive material. Since the FeSiB has excellent soft magnetic characteristics, the actuator with FeSiB was able to work in magnetic field strength of less than 10 kA/m. The theoretical formulas for the amount of the displacement and the force of the actuator were obtained. The theoretical results agreed with the experimental one. According to the theoretical formula, the displacement was calculated with the parameter of the mechanical properties of the substrate. To obtain the large displacement, the actuator with Co substrate was designed based on the theoretical formula. The displacement of 153 μm was obtained using Cu substrate of 1.1 μm thickness in the magnetic field of 10 kA/m. © 2008 Elsevier B.V. All rights reserved

Nanocrystalline Fe 87Zr 7Al 2B 3Cu 1 ribbons

A new nanocrystalline alloy with the nominal composition Fe 87Zr 7Al 2B 3Cu 1 was obtained directly from the melt-spinning process, in the ribbon shape. There is a positive influence of the as-quenched nanograins on the soft magnetic characteristics induced by the heat treatment of the as-cast material. The 2% Al addition determines the decrease toward zero of the saturation magnetostriction in the fully nanocrystallized samples and, as a consequence, the magnetoelastic anisotropy decreases giving rise to excellent soft magnetic characteristics ( μ e = 69.6 × 10 3 after optimum annealing of the as-quenched material). The magnetic and mechanical properties of the Fe 87Zr 7Al 2B 3Cu 1 ribbons are significantly improved by a two stages heat treatment: isothermal pre-annealing before the onset of the primary crystallization, for structural relaxation, followed by dc Joule heating, for the development of a more homogenous structure.

Magnetic properties of Ni1−x−yCoxFey films deposited by polyol electroless process

Electroless deposition using a nonaqueous, polyol process is carried out to produce nickel-rich Ni0.5Co0.5−xFex and cobalt-rich Co0.5Ni0.5−xFex (x=0, 0.1, 0.3, 0.5) ternary alloy films, and investigate the effect of incorporating iron on the morphology and magnetic properties of these two series of films. The plating solution used to deposit these films is prepared by mixing proportional volumes of equimolar metal salts suspended in ethylene glycol. Plating was performed by refluxing the nonaqueous solution at a temperature of 194 °C. The deposited films were characterized by electron microscopy, optical interferometry and X-ray diffraction. In the case of cobalt-rich films (Co0.5Ni0.5−xFex, x=0.0–0.5), a transition in the crystal structure from lower symmetric orthogonal to higher symmetric tetragonal or cubic structures was observed with increasing iron content. There was no such change for the nickel-rich films (Ni0.5Co0.5−xFex,x=0–0.5). The addition of iron was found to increase the surface roughness of both series of films. The magnetic measurements showed excellent soft-magnetic characteristics for as synthesized Co0.5Fe0.1Ni0.4 film with Ms, Hc, Ms⊥ and Hc⊥ values of 725.2 emu/cm3, 28 Oe, 205 emu/g and 176.5 Oe, respectively. The incorporation of iron was found to enhance the soft-magnetic characteristics of the otherwise weak magnetic Ni0.5Co0.5 film.

Effect of Pd addition on the magnetic characteristics of amorphous CoNbZr films

The goal of the present paper is to investigate the phase stability and soft magnetic properties of amorphous CoNbZr films when Pd is added. The CoNbZrPd films deposited on Si wafers exhibited amorphous structures independent of the amount of Pd. On the addition of 4.34% Pd, excellent soft magnetic characteristics of the films were observed with a coercive force of 0.54 Oe and an anisotropy field of 11 Oe, whereas a coercive force of 1 Oe and an anisotropy field of 3.5 Oe were shown in the film without the addition of Pd. The increased anisotropy field and low coercive force of the films may be attributed to the occupancy of Pd in preferred sites parallel to an external magnetic field applied during the deposition process. A permeability of about 1100 was constant at operation frequencies ranging up to 100 MHz, which can be explained by the Landau–Lifshitz formula.

磁性材料 ＭｎＺｎフェライト薄膜の微細構造に及ぼす熱処理雰囲気および添加物の効果

Manganese zinc ferrite thin films were prepared on quartz substrates buffered by a (00l) oriented ZnO underlayer by conventional rf magnetron sputtering method Mn-Zn-Fe oxide layers deposited on the ZnO underlayers were annealed in various atmospheres at 800°C for 5hours. When the films were annealed either at reduced pressure in air or in N2 gas flow, single phase spinel-type ferrite was formed. Manganese zinc ferrite films annealed in N2 gas flow had excellent soft magnetic characteristics compared with the films annealed at reduced pressure in air because of their remarkable grain growth. Furthermore, Bi2O3 and V2O5 were added for the purpose of inducing crystal grain growth. Manganese zinc ferrite films with Bi2O3 were improved in their saturation magnetization because of their grain growth and good crystallinity. On the other hand, manganese zinc ferrite films with V2O5 showed excellent soft magnetic characteristics, when vanadium of 0.51 at.% was added.

Ferromagnetic resonance in nanocrystalline Fe 73.5CuNb 3Si 13.5B 9 (Finemet)

The ferromagnetic resonance linewidth of Fe 73.5CuNb 3Si 13.5B 9 melt-spun ribbons has been investigated as a function of annealing temperature. Fe 73.5CuNb 3Si 13.5B 9 possesses an ultrafine grain structure which can be altered by suitable annealing to exhibit a combination of excellent soft magnetic characteristics and high saturation induction. It is a ferromagnetic metal consisting of crystallites whose anisotropy axes are randomly oriented and which may interact with each other via exchange or dipolar fields. When annealed at moderate temperatures, Fe 73.5CuNb 3Si 13.5B 9 is characterized by an extremely low coercive field, and is useful in magnetic cores and memories. At a critical temperature (∼600°C), the grain size rapidly increases with annealing temperature. This onset of crystallization is accompanied by a relatively abrupt increase in the FMR linewidth, the magnetic anisotropy field, and the coercive field. We extend the scaling arguments of Herzer to explain these obviously related phenomena.

Effects of Ar bombardment on magnetic properties of Fe films deposited by double-ion-beam sputtering

The microstructure and magnetic properties of polycrystalline Fe films have been investigated in detail by controlling the condition of ion-beam sputtering with an Ar bombardment with a constant ratio of arrival rate of Fe to Ar. To control the Fe crystallite size, Fe films have been deposited at an Ar bombardment voltage VA in the range of 80–2000 V with the condition that the ratios of the arrival rate RA (atoms of Fe/atoms of Ar) were 1 to 1 (RA of 1) and 1 to 0.1 (RA of 0.1). Fe films with excellent soft magnetic characteristics for 4πMs of about 21.5 kG and HC of 2.5 Oe were deposited on the substrate bombarded by Ar ions with VA of 200 V at Rs of 1 and 400 V at RA of 0.1. The Ar bombardment had the two effects of raising the local temperature of the film surface and decreasing the Fe crystallite size. The orientation of crystals in the films may be related to the bombardment energy and amount of Ar ions. The high-energy bombardment formed a mixing layer between the deposited film and the surface of the substrate. These results imply that Ar bombardment by the proper energy and amount of Ar ions assists in improving the soft magnetic properties in the films.

Improvement of soft magnetic properties of nanocrystalline FeMB (MZr and Nb) alloys and their applications

With the aim of developing good soft magnetic materials, we examined the magnetic properties of nanocrystalline FeMB alloys containing various additional elements. The nanoscale bcc FeZrNbBCu alloys exhibited excellent soft magnetic characteristics of 1.5 to 1.6 T for saturation magnetization (B s), 1 to 2 A/m for coercive force (H c), 10×10 4 to 12×10 4 for permeability (μ e) at 1 kHz and nearly zero saturated magnetostriction (λ s) which had not been achieved for soft magnetic materials reported up to date. The excellent soft magnetic characteristics have already enabled the practical use as pulse transformers for portable telephones which require high μ e above 10 5 at 1 kHz and high B s above 1.5 T. The application fields are hereafter expected to increase significantly because of the excellent soft magnetic properties which have been obtained only for the present materials.

Anomalous magnetic behaviour of nanocrystalline FeTaC films at high temperature

The magnetic properties of nanocrystalline Fe/sub 79/Ta/sub 10/C/sub 11/ films with different crystallographic characteristics are studied. The soft magnetic properties are not related to the Fe characteristics, but are closely related to the TaC characteristics, such as the lattice parameter and grain size. The film, composed of fine TaC grain with a small lattice parameter, has excellent soft magnetic characteristics at room temperature and its magnetic properties change little with temperature. On the contrary, the film composed of large TaC grain with a large lattice parameter has a large coercive force and magnetostriction at room temperature and exhibits a anomalous magnetic behavior at high temperature. The coercive force at 300 degrees C becomes ten times larger than that at room temperature. This phenomenon is most likely caused by the disappearance of the intergranular ferromagnetic coupling. >

Metallic glasses in distribution transformer applications: An update

Metallic glasses suffer substantially lower energy losses than their crystalline counterparts and, therefore, allow increased efficiencies of operation in transformers. This challenge posed by metallic glasses to the use of conventional, crystalline silicon steels as core materials in the manufacture of electrical distribution transformers has found increased recognition, internationally, among manufacturers and users of such transformers. This paper provides an update on the understanding of the behavior of these materials. The focus will be on the properties of Fe-rich metallic glasses, particularly the Fe-B-Si glasses, as these offer excellent soft magnetic characteristics and economic viability. The core loss characteristics of these materials will be discussed in some detail; a recent model for the loss mechanism will be reviewed. Results on the aging behavior of these metallic glasses will be presented, along with a model describing the aging behavior. Finally, the tendency of these materials to lose ductility following anneals will be addressed.

The influencing of sputtering alumina on the magnetics of hot-pressed Mn-Zn ferrite

Alumina was deposited on hot-pressed Mn-Zn ferrite by means of magnetron sputtering, and the changes in the magnetic properties of the ferrite were studied. It was found that the magnetic properties were improved. A layer with excellent soft magnetic characteristics was formed on the surface of the ferrite. >