Magnetic Properties Of Amorphous Alloys Research Articles

Effect of uniaxial stress on magnetic property of laminated amorphous sheets up to kilohertz range

Amorphous alloys are widely used as the core material for motors and transformers, which are subjected to stresses during manufacturing and operation processes. For instance, the compressive stress can influence the magnetic properties of amorphous alloys which leads to local overheating in the device and reduce the reliability. A high-frequency magnetizer with a stress application unit is designed and constructed to investigate the magnetic properties of amorphous alloys up to kilohertz range under stress conditions. The amorphous alloy sheets will fracture under stress because of their poor ductility and brittleness, so this paper uses laminated amorphous alloy sheets as the sample. The hysteresis loops and loss characteristics of amorphous alloys under stress ranging from 20 MPa tensile stress to 20 MPa compressive stress at a frequency of 50 Hz to 4 kHz are investigated. This research can provide data support for the design of cores in electromagnetic devices.

The Degree of Metallic Alloys Crystallinity Formed under Various Supercooling Conditions

Amorphous metal alloys play an important role in the electrical industry. Studies show the presence of an insignificant proportion of crystals in alloys that are amorphous from the point of view of X-ray diffraction analysis. The crystals significantly affect the mechanical and magnetic properties of amorphous alloys. Therefore, within this work, a comprehensive approach has been developed to determine the degree of crystallinity of amorphous alloys based on theoretical and experimental methods. The study is based on the mathematical model of supercooled melt crystallization previously developed by the authors, which takes into account the patterns of crystal formation and their diffusion and diffusionless growth, taking into account the mutual influence of growing crystals on each other. The mathematical model also takes into account the melt cooling mode when producing amorphous ribbons by cooling the melt on a rotating copper drum. The calculation results have been verified by experiments based on the new technique developed by the authors for calorimetric studies of amorphous ribbons. The developed methodology allows us to determine not only the average fraction of the crystals in a ribbon, but also the patterns of crystal distribution along its thickness as well as the patterns of changes in the proportion of the crystals in ribbons depending on the melt cooling mode.

Effects of Heat Treatment on some Magnetic Properties of Amorphous Alloys Containing Fe49Ni29Si9 B13 and Fe59Ni19Si9 B13

The effect of various processing modes on the magnetic properties of amorphous Fe49Ni29Si9B13 and Fe59Ni19Si9 B13 alloys obtained by melt spinning was examined. Samples from both alloys were prepared separately in the magnetic field and without the field. An increase in soft magnetic properties was observed during the period of the transition to the crystalline phase, (Hc = 50 A/m, Br = 2.16 Tl). After crystalline phases are formed, materials lose their soft magnetic properties. The composition of samples of rapidly cooled various Fe and Ni containing alloys were tested on XRD. Shimadzu XRD 6000 diffractometer was used to determine the phases of amorphous alloys by applying Cu Ka radiation at 40 kV/30 mA (CuKa1 = 122.59 A/m). Kβ radiation is eliminated by graphite monochromator

The effects of magnetic field intensity on the magnetic properties of Fe80Si9B11 amorphous alloys during magnetic annealing

Magnetic field annealing is an important method to enhance the magnetic properties of amorphous alloys. In this work, the effects of magnetic field annealing intensity on the magnetic properties, mechanical properties, and microstructure of Fe80Si9B11 amorphous ribbons were investigated. It can be seen from the results that the magnetic induction at 1600 A/m (B1600), maximum permeability (μm), coercivity (Hc), Elastic modulus (Er), and Hardness were improved with an increase of the magnetic field intensity. When the magnetic annealing intensity was 2.5 × 10−4 T, the B1600, μm, Hc, Er and Hardness of the sample were improved by 9%, 298%, 67%, 23% and 3%, respectively, compared with those of the as-spun sample. TEM results showed that there are some spherical symmetric clusters present in the 653 K × 2.5 × 10−4 T sample. This may be an important reason for the improvement of the magnetic properties. Compared with the 653 K × 1 T sample, the magnetic field intensity of the 653 K × 2.5 × 10−4 T sample was only 0.025%. However, the values of B1600, μm, Hc, Er and Hardness of the latter reached 96%, 82%, 115%, 90% and 94% of the former, respectively. It means that during the magnetic field annealing process, applying only a small magnetic field can obviously enhance the magnetic and mechanical properties of Fe80Si9B11 amorphous alloy. This provides a theoretical basis for the further improvement of the magnetic and mechanical properties of Fe80Si9B11 alloys, and in the energy saving. The reasons for the changes of magnetic and mechanical properties caused by different magnetic field intensities are discussed.

Effects of Annealing Temperature on Amorphous Co67Fe₃Cr₃B12Si15 Alloys for Flux-gate Magnetometers

The magnetic properties of amorphous alloy CoSUB67/SUBFe₃Cr₃BSUB12/SUBSiSUB15/SUB samples, which were produced by the melt-spinning method and annealed at various temperatures, are analyzed. We found the best annealing temperature for CoSUB67/SUBFe₃Cr₃BSUB12/SUBSiSUB15/SUB was 350 ℃ for 1 hour at 30 mTorr. We also produced a flux-gate magnetometer with the annealed samples with the best magnetic properties. The flux-gate sensor shows a noise level of 2.4 at pT√Hz 1 Hz, and 0.1 nTSUBp-p/SUB in the frequency domain with 1 Hz bandwidth.

Effects of Flux Treatment on the Glass Forming Ability and Magnetic Properties of Fe-based Ternary Amorphous Alloys

A series of Fe-P-B and Fe-Si-B amorphous alloys with high Fe contents exceeding 90 wt.% was successfully prepared by combining flux treatment and melt-spinning technique. The effects of Fe content and the flux treatment on the thermal and magnetic properties of amorphous alloys were studied. The glass-forming ability and the thermal stability of amorphous ribbons can be improved by a flux treatment, revealing the effective removal of heterogeneous nucleation sites in the ribbons through the flux treatment. It was found that Fe-Si-B ribbons exhibit higher saturation magnetization levels than Fe-P-B ribbons.

Magnetic properties of Co-based and Fe-based tape amorphous alloys

The description of the magnetic properties of amorphous alloys and comparison of the model evaluation with experimental data have been carried out in terms of the magnetic theory of disordered systems (Biryukov’s theory). The hysteresis loops for a number of amorphous metallic glasses have been investigated and it also has been shown that Biryukov’s hypothesis about the weak correlation between spin and electrostatic components is true for the amorphous magnetic system that permits to interpret collectively the results of different magnetometric experiments.

Two phase magnetic material modelling using two dimensional extended Preisach model

Abstract Extended Preisach model parameters can be strongly related to microstructural properties of material. It can also include real physical magnetization mechanisms such as domain wall motion and domain rotation. This paper shows that Preisach model is able to anticipate different phases in material structure. Existence of different phases in the material are due to thermal treatment, which is used to improve magnetic properties of amorphous alloys. Model was verified using ring shaped cores made of bilayered amorphous ribbons, which served as a physical model of the loosely coupled two phase ferromagnetic material with distinct magnetic properties.

Formability and magnetic properties of Dy-Co binary amorphous alloys

In this study, binary Dy-Co ribbons were synthesized by a conventional melt-spinning approach and glassy ribbons were successfully obtained within the compositional range Dy50Co50 to Dy68Co32. The glass formability and magnetic properties of these amorphous alloys were examined. The compositional dependence of glass formability, Curie temperature and magneto-caloric response of the DyxCo100-x (x=50, 55, 60, 65 and 68) amorphous alloys, as well as the mechanism involved, were determined.

Large variation of magnetic properties of amorphous Fe\u2013Zr thin films with Ar pressure during sputtering

A large change is observed in the magnetic properties of amorphous Fe–Zr thin films sputtered at different Ar pressures. The change depends on the composition of the alloys and at compositions near 60 at.% Fe, for example, the magnetisation measured at 10 kOe increases 30-fold with an increase in the Ar pressure from 2 to 10 mTorr. The magnetic properties are well explained by a combination of two phenomena—superparamagnetism and spin glass behaviours—and the large change is partly related to the number density of a magnetically correlated region. Examinations of the microstructure by X-ray diffraction, transmission electron microscopy, and X-ray absorption fine structure spectroscopy reveal no appreciable difference in it as a function of the Ar pressure. This indicates that even a very slight change in the microstructure can greatly affect the magnetic properties of amorphous Fe–Zr thin films, thereby opening up the possibility of employing the magnetic properties of amorphous alloys for the characterisation of amorphous microstructures.

The formation of hysteretic magnetic properties in amorphous alloys of various classes upon thermomagmetic treatment in a transverse magnetic field

In this paper, we have studied the effects of the thermomagnetic treatment in a transverse magnetic field (TMaT⊥) on the permeability of the amorphous alloy Co69Fe3.7Cr3.8Si12.5B11 with such a low saturation magnetostriction (λs 10–7) that, in the ribbons of this alloy rolled into a toroid, a sharp longitudinal magnetic texture is observed (Ksq > 0.90). It has been revealed that the permeability μ4 (H = 4 mOe, f = 1 kHz) as a function of the annealing temperature or time of holding at a temperature is described by a curve with a maximum. This maximum is observed at a coefficient of the squareness of the hysteresis loop Ksq,m in the range of 0.2 ≤ Ksq,m ≤ 0.4. The regimes of the TMaT have been determined that provide optimum values of the permeability μ4 (15000) without a loss of the ductile state of the ribbons of this alloy. Based on the example of an iron-based alloy of composition Fe57Co31Si2.9B9.1 with λs = 35 × 10–6, it has been shown that the formation of the hysteretic magnetic properties upon the TMaT⊥ depends substantially on the magnitude of the magnetostriction and the Curie temperature of the amorphous alloys.

Effect of annealing on the structural and magnetic properties of (Fe1−xCox)83B17 metallic glasses

Abstract Amorphous alloys of (Fe 1− x Co x ) 83 B 17 ( x =22, 25.3, 28.4) in the vicinity of 25 at% of Co were prepared by melt spun technique. The samples were annealed at different temperatures and the changes in structural and magnetic properties have been studied. Phase stabilization and magnetic properties of amorphous alloys were studies using X-ray diffraction and Mossbauer spectroscopy. The result shows anomalies in structure and in magnetic properties in the studied samples. Annealing at 475 °C brings about the formation of complete and stable crystalline structure. At this stage multiple crystalline phases have been observed. Mossbauer spectroscopy also revealed that two phases of Fe 3 B were formed along with stable Fe 3 Co phase.

Influence of Annealing on the Microstructure and Magnetic Properties in Amorphous Alloys

Abstract The influence of isothermal annealing on the magnetisation process in strong magnetic fields of the amorphous Fe61Co10Y8Ni1B20 alloy ribbons was investigated. Samples in the form of ribbons were produced by rapid quenching of liquid alloy on a rotating copper wheel. In order to study the relaxation process, the investigated Fe61Co10Y8Ni1B20 samples were subjected to annealing below the crystallisation temperature at 700 K for 1 h and then at 770 K for 3.5 h. The structure of the samples was examined by X-ray diffraction measurements (XRD). It was found, that all of measured samples in the as-cast state and after thermal treatment, were amorphous. On the basis of virgin magnetisation curve analysis, the type, size and density of structural defects occurring in the investigated samples were determined. It was found that after the first stage of annealing, decay of linear defects (pseudo-dislocation dipoles) into smaller, more thermodynamically stable, point defects occurs. The presence of point like defects was also confirmed after the second stage of annealing.

Effect of manufacturing method on the magnetic properties and formation of structural defects in Fe61Co10Y8Zr1B20 amorphous alloy

Soft magnetic properties of amorphous alloys are determined by their structure, which strongly depends on their manufacturing method. Alloys obtained in the form of conventional amorphous alloys (tapes) are cooled with a much higher rate than the material obtained in the form of tiles by the injection casting method. The cooling rate and production method determines the type and number of structural defects created in the volume of produced samples. The paper presents an indirect method for the analysis of structural defects and their effect on the magnetic properties of studied alloys. Basing on initial magnetization curve analysis in the area of so-called approach to ferromagnetic saturation was found that point defects were forming in the samples in the form of tapes. The magnetization process of tiles were influenced by the presence of conglomerates of point defects called quasidislocation dipoles.

Magnetoelastic effects in amorphous alloys

The domain structure and properties of amorphous ferromagnetic alloys are studied. The magnetic properties of amorphous alloys may be effectively regulated by creating a specific quasi-structure based on magnetoelastic effects.

Effect of the High Pressure Torsion on Magnetic Properties of Amorphous Alloys

The effect of severe plastic deformation in Bridgman’s chamber on magnetic properties of the amorphous alloys of metal-metalloid type Ni44Fe29Co15Si2B10, Fe50Ni33B17, Fe70Cr15B15 obtained by the melt quenching was studied. The substantial alteration of saturation magnetization depending on the number of ferromagnetic and antiferromagnetic components in the alloy was revealed. It was supposed that the internal separation into nanoscaled areas enriched and depleted by ferromagnetic components took place in the amorphous matrix under the action of severe plastic deformation.

Simulation of magnetic phase transitions in amorphous alloys of the Re-Gd system

Using the Monte Carlo method within the Heisenberg model, we studied the magnetic properties of amorphous alloys of the Re-Gd system and of pure amorphous gadolinium. The temperature dependences of spontaneous magnetization, magnetic susceptibility, and the Edwards-Anderson order parameter were determined. The possibility of the system transitioning to the spin-glass state was examined.

Severe plastic deformation of amorphous alloys: II. Magnetic properties

The influence of severe plastic deformation in a Bridgman cell on the magnetic properties of amorphous alloys of metal-metalloid type, Ni44Fe29Co15Si2B10, Fe74Si13B9Nb3Cu1, Fe57.5Ni25B17.5, Fe49.5Ni33B17.5, and Fe70Cr15B15, obtained by melt spinning, has been investigated. It is found that the saturation magnetization significantly changes (increases or decreases), depending on the number of ferromagnetic and antiferromagnetic components in the alloy. It is suggested that very high shear stress causes internal phase decomposition in the amorphous matrix into nanoscale regions, enriched or depleted with ferromagnetic components.

Monte Carlo simulation of magnetic phase transitions in amorphous alloys of the Re-Tb system

The magnetic properties of amorphous alloys of the Re-Tb system and pure amorphous terbium have been investigated by the Monte Carlo method within the Heisenberg model. The temperature dependences of the spontaneous magnetization and magnetic susceptibility have been constructed for different ratios of the anisotropy constant to the exchange constant, D/J. The minimum value of D/J at which the spin-glass transition occurs is determined. The magnetic phase diagram of amorphous Re-Tb alloys, obtained by the simulation, is in qualitative agreement with the experimental data.

Influence of alloying additions and annealing time on magnetic properties in amorphous alloys based on iron

The present paper focuses on the influence of alloying additions on magnetostriction coefficient, concentration of free volume and magnetization in Fe–X–Si–B, and Fe–X–Cu–Si–B amorphous alloys. It was shown that in one group of alloys, the enhancement of soft magnetic properties effect can be attributed to formation of nanocrystalline phase αFe(Si), a decrease of the magnetostriction coefficient and annealing out of free volume. In the second group of alloys, this effect is due to a decrease of the magnetostriction coefficient and annealing out of free volume i.e. takes place in the relaxed amorphous phase.