Structural, magnetic characterization (dependencies of coercivity and loss with the frequency) of magnetic cores based in Finemet (original) (raw)
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Magnetic Characterization in the Rayleigh Region of Nanocrystalline Magnetic Cores
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We report on the structural and magnetic characterization of two nanocrystalline Finemet-type magnetic cores. The nanocrystalline structure developed after annealing the amorphous precursor alloy at 550 °C for 30 and 60 min of annealing time. Structural analysis carried out by means of X-ray diffraction providing useful information on the grain size mean and partial volume of the nanocrystalline phase. The magnetic characterization was focused mainly in the Rayleigh region which, influenced by the intergranular coupling, was found to be more efficient in the sample treated for a longer time with a finer nanocrystalline structure.
2015
International audienceNowadays, nanocrystalline soft magnetics materials for high power applications receive more and more consideration. Nevertheless, some technological parameters can have an influence of potential significance on the performances (losses, permeability, frequency behavior…). One main drawback of the nanocrystalline materials is their brittleness. To prevent this effect in order to handle the Magnetic Circuit (MC), it is preferable to impregnate it with varnish. Moreover, thanks to the impregnation, the MC can be cut in order to insert the winding. In this paper, the influence of various technological manufacturing processes on the magnetic properties of nanocrystalline cores is studied. Firstly, nanocrystalline magnetic cores of the same size, without impregnation and with three different varnishes, are experimentally characterized with a hysteresigraph (from DC to 1 MHz). Secondly, the same MC were cut in and characterized again. This protocol gives information a...
Magnetism of nanocrystalline Finemet alloy: experiment and simulation
The European Physical Journal B - Condensed Matter, 2003
Mössbauer spectrometry and magnetic measurements are employed to experimentally investigate the magnetic behavior of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 ribbons obtained by appropriate annealing of the amorphous precursor. A detailed analysis of the correlation between the microstructure of annealed samples and their magnetic properties is provided. Thermomagnetic data allow the Curie temperatures of both amorphous residual matrix and nanocrystalline phase to be estimated. The differences between Curie temperatures of amorphous residual matrix and amorphous precursor are investigated and explained in terms of magnetic polarization of the matrix by exchange fields arising from the nanocrystalline grains. Theoretical systems of spins consisting of a single ferromagnetic nanocrystalline grain immersed in weakly ferromagnetic environment, quite similar to our real samples, are considered and their magnetic behavior is investigated by Monte Carlo simulation of low temperature spin ordering, with emphasize on the matrix-nanocrystalline grain interface which is shown to exhibit peculiar magnetic behavior. The magnetic features of the matrix-nanocrystalline grain interface are studied, as depending on matrix-nanocrystalline grain exchange coupling as well as crystalline fraction of the nanocrystalline systems. PACS. 81.07.Bc Nanocrystalline materials -75.30.-m Intrinsic properties of magnetically ordered materials -75.75.+a Magnetic properties of nanostructures
IEEE Transactions on Magnetics, 2000
In this work, we have investigated the effect of a transversal applied DC magnetic field on the longitudinally measured magnetic properties of nanocrystalline Finemet cores. The core was prepared by stacking up toroidal sheets (,) cut from 20 mm wide Finemet ribbon of 22 m thickness. The resulting height of the toroid was 5 mm. The stack was heat treated in hydrogen at 550 for 1 h. Quantitative measurements were conducted by using a Helmholtz coil for generating the transversal field along the ring axis so that the magnetization of the toroidal core is forced to turn out of the sheet, transversal to the measuring magnetic field applied along the toroid. Flattening of the quasi-static loop as a function of transversal field is accompanied by a diminution of the remanence and coercive field. The relative permeability could be diminished by more than two orders of magnitude (from 60 000 to 700). Correspondingly, the eddy current frequency limit (where the imaginary part of the permeability is maximal) was shifted from 60 kHz to 1 MHz. Tayloring the hysteresis loop will be discussed in terms of rotational magnetization which dominates over the domain wall displacement mechanism when the magnetization is forced to turn out of the sheet plane.
Physica B: Condensed Matter, 2001
FeNbCuSiB metallic glasses show excellent soft magnetic properties in nanocrystalline state such as high saturation induction and permeability, low magnetostriction, coercive field and anisotropy, which make these materials very suitable for use in magnetic devices or sensors based on magnetoimpedance (MI) effect. The main aim of this paper is to emphasise the great importance of structure characterisation when a complete understanding of the magnetic behaviour is pursued. In this way, we present an exhaustive study of the correlation between the magnetic properties and the structural changes occurring along the crystallisation process, focusing our interest on the first stages of the crystallisation, where magnetic parameters, such as the magnetic permeability or the Curie temperature of the amorphous matrix, together with magnetic domain structure undergo more sensitive changes. Several experimental results obtained by means of X-ray and neutron diffraction, differential thermal analysis, thermomagnetization, M .
Structure and soft magnetic properties of Finemet alloys
Journal of alloys and …, 2000
The soft magnetic properties of Fe Cu Nb Si B (Finemet) alloys prepared by mechanical alloying were studied using various 73.5 1 3 13.5 9 experimental techniques including Mossbauer spectroscopy. The study includes the influence of the milling atmosphere. The results are compared with mechanically alloyed Fe-Si alloys as well as with melt-spun Finemet alloys. The coercivity of the mechanically alloyed powder is much larger than that of the melt-spun ribbons, though the saturation magnetisation is the same. This is ascribed to the absence of a grain boundary amorphous ferromagnetic phase resulting in a weakening of the exchange coupling between the nanograins. This study suggests that the interfacial component in Finemet alloys plays a crucial role in achieving good soft magnetic properties. The critical grain size for single domain particle was found to be 10 nm. For very small grain sizes, the existence of superparamagnetism was alsö studied using Fe-57 Mossbauer spectroscopy.
Journal of Magnetism and Magnetic Materials, 2013
With the development of modern ferromagnetic technology, soft magnetic powder cores (MPCs) of amorphous and nanocrystalline alloys have been intensively studied for their excellent soft magnetic properties such as high flux density, low coercivity and reduced core loss due to amorphous state and nanocrystalline grains of 10-20 nm dispersed in a residual amorphous matrix. In this paper, the microstructures and soft magnetic properties, i.e., maximum magnetic induction B m , effective permeability m e , DC-bias properties and volume power losses P CV of MPCs made from amorphous powder of gas atomization and nanocrystalline powder of pulverized melt-spun ribbon were investigated and also compared on the basis of the same level of m e . It is found that m e of both kinds of MPC keeps unchanged up to 1 MHz. The amorphous MPC has lower P CV at lower frequency range, while the nanocrystalline MPC has lower P CV at high frequency range instead. Also, the nanocrystalline MPC has better DC-bias property. Moreover, the DC magnetic properties and the changes of P CV of both MPCs with frequency and flux density are also studied. Furthermore, the electromagnetic characteristics, the microstructures and the mechanisms accounting for these phenomena of both MPCs are also discussed.
High performance of low cost soft magnetic materials
Bulletin of Materials Science, 2011
ABSTRACT The consistent interest in supporting research and development of magnetic materials during the last century is revealed in their steadily increasing market. In this work, the soft magnetic nanocrystalline FINEMET alloy was prepared with commercial purity raw materials and compared for the first time with the generally studied high purity one. The exhaustive characterization covers several diverse techniques: X-ray diffraction, Mössbauer spectroscopy, differential scanning calorimetry, differential thermal analysis and magnetic properties. In addition, a brief economic analysis is presented. For the alloys annealed at 813 K, the value of the grain size was 16 nm with 19·5% of Si, the coercivity was 0·30 A m−1 while the saturation was 1·2 T. These results prove that structural, magnetic and thermal properties of this material are very close to the expensive high purity FINEMET alloy, while a cost reduction of almost 98% seems highly attractive for laboratories and industry. The analysis should be useful not only for the production of FINEMETs, but for other type of systems with similar constitutive elements as well, including soft and hard magnetic materials.
Optimization of soft magnetic properties in nanoperm type alloys
Materials Science and Engineering: C, 2003
In the present paper, it was shown that soft magnetic properties of the group of amorphous alloys Fe -X 2 -B 22 (X = Cr, Zr and Nb) can be optimized (magnetic permeability increases about five times) by applying 1-h annealing at temperatures: 600, 600, 650 and 700 K for the Fe 78 B 22 , Fe 76 Cr 2 B 22 , Fe 76 Zr 2 B 22 and Fe 76 Nb 2 B 22 alloys, respectively. This effect is attributed to annealing out of free volumes formed into material during fabrication and for the Fe 76 Zr 2 B 22 alloy also to a formation of a nanocrystalline phase. Using isothermal measurements of magnetization (magnetic balance), it was shown that the process of formation of nanocrysalline phase can be described by Johnson -Mhel -Avrami kinetic. Activation enthalpy of this process was deduced as 3.2 eV and the power law exponent 3.4. D
Microstructure and Magnetic Properties of NANOPERM-Type Soft Magnetic Material
Acta Physica Polonica A, 2019
In recent years, amorphous and nanocrystalline Fe-based alloys, due to their unique soft magnetic properties, have emerged as one of the most promising group of modern materials for various electric applications. This work presents microstructure and AC/DC magnetic properties of the NANOPERM-type material. The as-quenched amorphous Fe76Mo8Cu1B15 alloy was prepared by rapid quenching method in a form of 10 mm wide and 0.025 mm thick ribbon. Partial nanocrystallization was obtained by subsequent annealing of amorphous precursor at 783 K for 30 min. Microstructure investigation of annealed sample confirmed precipitation of α-Fe nanograins dispersed in amorphous matrix. In order to assess soft magnetic properties of fabricated material the dependences of core losses versus frequency (50 Hz-20 kHz) at room temperature were established, together with eddy currents, hysteresis, and anomalous losses coefficients separation. The frequency dependent correlation between real and imaginary part of permeability was also presented. Moreover, DC hysteresis loops of both as-quenched and annealed alloy were recorded in temperature range from 200 K to 400 K.