Soft Magnetic Amorphous Alloys Research Articles

Magnetoelectric effects in piezoelectric/soft magnetic amorphous FeCo-based ribbon composites

Magnetoelectric effect has been investigated in several multiferroic laminates generated by inserting a lead-zirconate titanate PZT plate between sheets of highly soft magnetic amorphous FeCo-based alloy ribbon. The results show that the magnetoelectric coefficient αE (= dE/dH) depends on the rest glass-forming elements as well as the concentration of Co substitution. Giant magnetoelectric is found for the composite of Fe73.5Cu1Nb3B9Si13.5 ribbon, where αE as high as 1000 mV/cmOe at low field of 50 Oe. aE can be further improved up to 1170 mV/cmOe at 20% Fe substituted by Co. The higher the Co concentration, the lower magnetoelectric effect is observed. High magnetoelectricty at low field makes these composites suitable for special applications such as smart sensors for detecting microtesla magnetic fields and especially biosensor for magnetic label detection.

Study of Magnetic Inhomogeneity on the Magnetoimpedance Effect of Soft Magnetic Alloys

There are various annealing techniques to influence the magnetic anisotropy of amorphous soft magnetic alloys, applicable for magnetic sensing elements. Laser irradiation of amorphous magnetic ribbons is a kind of annealing method to affect their magnetic moment orientations and consequently change their magnetic anisotropy and magnetoimpedance effect. In this paper, we have studied the role of magnetic anisotropy in the magnetoimpedance effect of laser annealed amorphous ribbons. In our theoretical study, we took into account the variations of magnetic anisotropy constants of local magnetic moments after annealing process. We showed that the flatten magnetoimpedance response which was observed in the experiments can be justified by averaging different local anisotropies induced by laser processing.

Rapid nanocrystallization of soft-magnetic amorphous alloys using microwave induction heating

The crystallization of Fe73Nb3Cu1Si16B7 alloy during microwave heating was investigated in situ using synchrotron radiation powder diffraction. The phase transformation comprises a primary nanocrystallization stage and a final microcrystallization step. We provide evidence for a strong enhancement of the transformation kinetics. Microwave heating occurs as a result of both ohmic and magnetic losses induced by eddy currents, which defines a volumetric microwave induction heating process. Nanocrystallization is completed within 5 s, while full crystallization is achieved in less than 10 s.

Study on Preparing and Crystallization Kinetics of Melt-Spun Co-Based Soft Magnetic Amorphous Alloy

Abstract Amorphous ribbons of Co 68.5 Fe 4 Si 10 B 17.5 were prepared by a single roller melt-spinning technique in the air atmosphere. The crystallization products were analyzed by X-ray diffraction. The crystallization kinetics of the alloys were investigated by means of differential scanning calorimetry (DSC) in the mode isothermal annealing. It is found when the isothermal kinetics was modeled by the Johnson–Mehl–Avrami equation, the Avrami exponents are calculated to be in the range of 2.11–2.58 for different isothermal temperatures. This implies that the crystallization of Co 68.5 Fe 4 Si 10 B17.5 amorphous alloy is governed by either diffusion or interface controlled three-dimensional growth, depending on the annealing temperature. On the basis of the Arrhenius relation, the activation energy E c in the isothermal process is calculated to be 113.67 kJ/mol. Finally, details of the nucleation and growth behaviors during the isothermal crystallization are discussed.

Phase evolution and field-induced magnetic anisotropy of the nanocomposite three-phase fcc, hcp, and amorphous soft magnetic alloy Co89Zr7B4

Crystallization and field-induced magnetic anisotropy were investigated for a Co89Zr7B4 alloy. A mixture of nanocrystalline fcc and hcp phases surrounded by an amorphous matrix is present after primary crystallization. For annealing in a 2T transverse field, the observed anisotropy fields and field-induced anisotropies are HK∼12–15Oe and KU∼550–680J∕m3 for field annealed amorphous ribbons as compared to HK∼18–19Oe and KU∼800–850J∕m3 for field crystallized ribbons. In comparison with the corresponding Fe-based alloy, the relatively high Curie temperature and large field-induced anisotropy of the field annealed amorphous ribbons indicate that the intergranular amorphous phase may provide a relatively more significant contribution to the field-induced anisotropy of Co-based nanocomposite ribbons such as Co89Zr7B4.

Effect of Mn Substitution on the Structure and Microwave Properties of Nd-Fe-B Nanocomposites

The influence of Mn content on the structure and magnetic permeability of Nd3Fe68-xMnxCo18B11 (x = 0, 1, 2) amorphous soft magnetic alloys was studied. The ribbons were prepared by melt-spining. The permittivity–frequency and permeability–frequency properties were determined in the microwave frequency regime of 2-18 GHz by vector network analysis. XRD spectra showed that only α-Fe diffraction peak was observed in the as-spun alloy. It is found that the acquired complex permittivity and permeability values match the microwave frequency when the 1at% Mn content doped. The results suggest a new design of microwave absorbers based on electromagnetic wave absorbing materials.

The magnetocaloric effect in soft magnetic amorphous alloys

The influence of different compositional modifications on the magnetic entropy change and refrigerant capacity of Finemet, Nanoperm, HiTperm, and bulk amorphous alloys is presented. For all the studied alloys, the field dependence of the magnetic entropy change exhibits a quadratic dependence in the paramagnetic regime, a linear dependence in the ferromagnetic temperature range, and a potential law with a field exponent ∼0.75 at the Curie temperature. This exponent can be explained using the critical exponents of the Curie transition. It is shown that for alloys of similar compositional series, the magnetic entropy change follows a master curve behavior.

In situ X-ray diffraction investigation of nanocrystallization of amorphous Co–Fe–Zr–B alloys

Cobalt-rich soft-magnetic alloys were recently developed as amorphous materials with promising engineering properties, e.g. high mechanical strength, excellent magnetic properties and high corrosion resistance. The crystallization of the as-prepared amorphous alloys plays a crucial role in most technological applications of these advanced soft-magnetic nanomaterials. Amorphous ribbons with nominal composition Co 56Fe 16Zr 8B 20 (at%) were here obtained by single-roller melt spinning. The nucleation and growth of nanoscale phases during constant-rate heating of as-quenched and of high-energy ball-milled Co-rich amorphous soft-magnetic alloys were investigated by differential scanning calorimetry and by in situ high-temperature powder X-ray diffraction using synchrotron radiation. The temperature/time evolution of the crystallite size and of average microstrain was obtained from the X-ray diffraction line-profile analysis (LPA) of the powder diffraction patterns.

Employment of the artificial neural networks for prediction of magnetic properties of the metallic amorphous alloys

The aim of this work is to employ the artificial neural networks for modelling the magnetic properties of the amorphous alloys with the iron and cobalt matrix. The artificial neural networks implemented in StatSoft Statistica Neural Network PL 4.0F were used to determine the relationship between the chemical compositions of amorphous alloys, heat treatment parameters and magnetic properties. The attempt to use the artificial neural networks for predicting the effect of the chemical composition and heat treatment parameters on the magnetic flux density BS succeeded, as the level of the obtained results was acceptable, as the level of the obtained results was acceptable. For different magnetic properties of soft magnetic materials, further calculations are planned. The results of calculation makes it possible to design new advantageous combinations of concentrations of the particular elements to develop grades of the soft magnetic alloys. This paper employs the artificial neural networks for modelling chemical composition and heat treatment parameters of amorphous soft magnetic alloys to obtain the best magnetic properties. [Received 15 August 2007; Accepted 20 October 2007]

Field dependence of the magnetocaloric effect in materials with a second order phase transition: A master curve for the magnetic entropy change

The field dependence of the magnetic entropy change can be expressed as ΔSM∝Hn. For soft magnetic amorphous alloys n=1 well below the Curie temperature (TC), n=2 in the paramagnetic range, and n≈0.75 for T=TC. The first value can be explained with simple arguments, n=2 is a consequence of the Curie-Weiss law, but n(TC) deviates from mean field predictions. From the Arrott-Noakes equation of state, a relation between n(TC) and the critical exponents has been obtained, showing remarkable agreement with experimental data (for an example alloy, predicted n=0.72 versus experimental n=0.73). A master curve behavior for the temperature dependence of ΔSM measured for different maximum fields is proposed.

Refining the formation of nanocrystals in soft magnetic amorphous alloy via EXAFS spectroscopic analyses

The amorphous metallic alloy with the composition Fe73.5 Nb3Cu1Si13.5B9 is now quite well known as FINEMET, mainly owing to its excellent magnetic properties that are supposed to be due to the formation of small nanocrystals consisting of Fe and Si, i.e., DO3 phases, during simple heat treatment [1–3]. The evolution of such nanocrystals and their effects on the magnetic properties were comprehensively described in previous reports [4–6]. With using mainly the Fe K-edge and Cu K-edge EXAFS spectra, Ayers et al. carefully studied nucleation kinetics of samples that were heat-treated at various durations [7, 8]. In particular, the role of Cu on nucleation processes in this noncrystalline metal was largely proven by experimental observations of a series of Fourier-transformed EXAFS spectra taken at the Cu K-edge of differently heat-treated samples. A key point in their nucleation model for this amorphous metal is that Cu clusters act as nucleation sites of the DO3 nanocrystallites [8]. It is noteworthy that not all Cu atoms are involved in the generation of the DO3 nanocrystals. Nonetheless, Ayers et al.’s analyses were generally qualitative since they explained the local structural evolution of Cu based on the fingerprint comparison between the partial radial distribution functions of the samples. Thus, though successful, their analyses did not give a quantitative fraction of Cu participating in the nucleation processes of DO3 nanocrystals in their samples. This study sought to come up with a quantitative refinement of the local structures of copper atoms in the amorphous metals. Specifically, the Cu K-edge EXAFS spectra of three representative specimens, i.e., single crystalline Cu (designated SC hereafter), as-quenched Fe73.5Nb3Cu1Si13.5B9 (AQ) and the other one heattreated for 1 h (HT), were recorded. The fraction of the Cu atoms that remained amorphous without playing a role in the nucleation of the Fe-rich DO3 precipitates was then determined.

METGLAS ALLOY 2605 SA1

Abstract Metglas 2605 SA1 is an amorphous iron-base soft magnetic alloy designed for extremely low core loss at distribution and power transformer frequencies and inductions. Applications include high-frequency inductors and current transformers. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on casting, forming, and heat treating. Filing Code: FE-139. Producer or source: Metglas Inc.

Influence of External Factors on Amorphous and Nanocrystalline Soft Magnetic Alloys Studied by Mössbauer Spectroscopy

In this paper, a review of recent 57Fe Mössbauer spectroscopy (MS) studies of external influence on the properties of amorphous and nanocrystalline Fe- and Co-based alloys is submitted. Different types of alloys (FeCuNbZr, FeCuNbSiB, FeCoCuNbB, CoFeZrB and CoFeSiB) in the form of original amorphous and nanocrystalline ribbons were subjected to different external factors: different annealing atmospheres, mechanical stress (for example influence of ball-milling) and tensile stress. It will be shown that the Mössbauer spectrometry is a suitable tool for such studies because the measured spectral parameters are very sensitive to the changes in the vicinity of the probe 57Fe-nuclei and thus, this technique provides a wide variety of information about structural and magnetic behavior of Fe-containing materials.

Magnetic relaxations in amorphous soft magnetic alloys

The paper reviews selected results of the extended experimental investigations of magnetic properties, time–temperature stability and workability of the soft magnetic amorphous alloys controlled by structural magnetic relaxation. Complex approach to the magnetic relaxations in multicomponent amorphous alloys is presented. The transition from magnetic after-effect to a new MAE spectrometry is illustrated on ternary amorphous CoSiB alloy.

New FeNbB-based bulk amorphous and nanocomposite soft magnetic alloys

This paper deals with results on preparation and magnetic characterization over a wide frequency range of (Fe,Co,Ni)/sub 70/Nb/sub 10/B/sub 20/ new bulk amorphous and nanocomposite alloys. Their structure is either fully amorphous or consisting of very fine 5-10 nm /spl alpha/-Fe(Co) particles dispersed within the amorphous matrix. Saturation inductions of about 0.85 T, relative permeabilities of 7/spl times/10/sup 4/ (at 80 Hz), and coercive fields of 40 A/m are determined for new Fe-Nb-B-based bulk amorphous torroids, whereas in nanocomposite cast bars, H/sub c/ varies between 180 and 360 A/m in the as-cast state and decreases by about half when the refined nanocrystalline structure is achieved. In the frequency range 50 Hz to 2 kHz, magnetic permeability decreases from 7/spl times/10/sup 4/ to 0.5/spl times/10/sup 4/. The potential impact of these materials on engineering applications is presented in connection with their specific magnetic behavior and casting ability.

Change in soft magnetic properties of Fe-based metallic glasses during hydrogen absorption and desorption

The stress level can be altered in soft magnetic amorphous alloys by hydrogen absorption. The resulting changes in the soft magnetic parameters are reversible or irreversible, depending on the chemical composition. Some of these effects are demonstrated in Fe–B, Fe–W–B, and Fe–V–B glassy ribbons, in which various magnetic parameters are measured mainly during hydrogen desorption. The rate of hydrogen desorption is also monitored by measuring the pressure change in a hermetically closed bomb. The observed phenomena are interpreted on the basis of induced stresses and chemical interactions between the solute metal and hydrogen.

Anisotropies in soft magnetic nanocrystalline alloys

The article reviews and updates the understanding of the soft magnetic properties of nanocrystalline Fe-based alloys. In optimized compositions the random magneto-crystalline anisotropy of the structural phases is largely averaged out. The soft magnetic properties are then controlled by magneto-elastic and induced anisotropies which are uniform on a scale much larger than the exchange length. But unlike to the case of soft magnetic amorphous alloys, there is still a competition between the random and the more uniform anisotropy contributions. The experimental findings are complemented by theoretical results.

In situ detection method for obtaining permeability of Fe-based amorphous alloys: ac resistance measurement for Fe84Nb7B9

In this letter, we propose an in situ detection method for obtaining permeability of soft magnetic Fe-based amorphous alloys. The temperature dependence of ac resistance was measured at different frequencies during heat treatment of Fe84Nb7B9 amorphous alloys. A significant increase in the ac (∼1000kHz) resistance appears at around 920 K during the heating process, which arises from the skin effect caused by a marked increase in sample permeability. This skin effect diminishes when the sample is heated to approximately 1100 K, which corresponds to the decrease in its permeability. Consequently, we note that the ac resistance measurement is useful for quick in situ assessment to achieve the soft magnetic property of an Fe-based amorphous alloy.

Dynamic Compacting of Powders of Some Amorphous Alloys

AbstractAt present amorphous metallic alloys have the broad expansion in various fields of science&engineering as a result of their unique properties. In particular, soft magnetic amorphous alloys are extensively used in electrical engineering. However the production of considerable-size nonporous wares based on the powders (or tapes) of these alloys is heavy problem owing to high hardness of the particles. Therefore shock wave’s compacting or Dynamic Compacting (DC) method is promising one to produce the wares on the base of powders of amorphous alloys because it can provides high strength and near zero porosity of the wares. The experimental D-U diagrams of soft magnetic amorphous alloys were obtained to realize this method of compacting. The calculations of the amplitude and duration of shock wave were carried out. The several versions of explosive devices using shock plane wave generator to produce circular magnetic conductors were developed and were tested. These magnetic conductors are based on amorphous alloys of 5BDSR, GM414, 10NSR trademarks (Fe with Cu, Nb, Si, B additives). XRD analysis proved that amorphous state of the alloys remains the same up to 20 GPa shock wave’s pressures. The mechanical, structural, electrical and magnetic properties both initial amorphous alloys and compacted one were obtained and compared as a result of the implemented works. It was stated that DC leads to increase of magnetic conductivity by factor ∼15 with respect to initial amorphous alloys powder. Besides the specific losses decrease in ∼4 times.

Synthesis, Preparation and Properties of New Fe-Based Soft Magnetic Amorphous Alloys with a Large Supercooled Liquid Region

Synthesis, Preparation and Properties of New Fe-Based Soft Magnetic Amorphous Alloys with a Large Supercooled Liquid Region