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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic power losses have been experimentally investigated and theoretically predicted over a range of frequencies (direct current—1.5 kHz) and peak inductions (0.5–1.5 T) in 1-mm-thick FeSi 2 wt. % laminations. The direct current hysteresis properties of the system are described by the Preisach model, with the Preisach distribution function reconstructed from the measurement of the recoil magnetization curve (Bp=1.7 T). On this basis, the time behavior of the magnetic induction vs frequency at different lamination depths is calculated by a finite element method numerical solution of Maxwell equations, which takes explicitly into account the Preisach model hysteretic B(H) relationship. The computed loop shapes are, in general, in good agreement with the measured ones. The power loss dependence on frequency is predicted and experimentally found to change from a ∼f3/2 to a ∼f2 law with increasing peak induction. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5371-5379 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new model is presented which quantitatively describes the reversible magnetization process and its contribution to the magnetization curve in soft amorphous ribbons. It takes into account the role of the coherent moment rotations, through analysis of the orientation distribution of the magnetization vector Is in the sample cross section and its evolution with the applied field. Such analysis relies on the assumption, dictated by magnetic domains observations, of a spatial distribution of local anisotropies, whose intensity and direction are mainly determined by the long-range random stresses quenched in during the process of rapid solidification. The reversible I(H) curve is obtained by integrating the local magnetization contributions with respect to their angular distribution, according to a minimum energy condition involving the Zeeman, the local anisotropy, and the macroscopic anisotropy terms. It is shown that a relatively simple analytical expression for I(H) can be worked out. The model is applied to experimental I(H) recoil curves, which have been determined as a function of the stress-induced anisotropy in positive magnetostriction (Fe81B14Si3C2) and negative magnetostriction (Co80B10Si10) amorphous ribbons. It is shown that the shape of I(H) and its evolution with the applied tensile/compressive stress are correctly predicted by the theory.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4045-4047 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hysteresis loop and loss properties of near-zero-magnetostrictive amorphous ribbons have been investigated as a function of the induced macroscopic magnetic anisotropy Ku from dc to 10 kHz. It is found that, following the evolution of Ku, imposed by means of sequential field annealings along the longitudinal (LD) and transverse (TD) directions, the hysteresis loop shape and area and the frequency dependence of energy losses suffer dramatic changes, dictated by the value of Ku and the local distributed anisotropies K. On passing from longitudinal to transverse macroscopic easy axis, coherent spin rotations come into play and, in association with the domain wall displacements, eventually provide a net magnetization reversal along both LD and TD. The hysteresis loss component Wh correspondingly increases and the energy loss at high frequencies decreases. It is concluded that: (1) optimal quasi-static magnetic behavior requires relatively high and positive Ku values (〉50–100 J/m3), with longitudinal plane rigid walls and (2) the best high frequency properties are attained for Ku∼0, where flexible walls and complex domain patterns are created. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5020-5022 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of stress-induced anisotropy on magnetic power losses has been investigated in FeBSiC amorphous ribbons, in the "as-quenched'' state and after annealing. Loss separation has been accomplished up to 400 Hz, under a wide range of applied tensile stresses (3.5 MPa≤σ≤300 MPa). It is found that, by increasing σ, the hysteresis loss component Wh is initially decreased and passes through a minimum around a critical stress σ0. Correspondingly, rearrangement of the maze domain structure associated with the unstressed state occurs and a longitudinally oriented pattern sets in. The dynamic loss exhibits a somewhat opposite trend, as it tends to monotonically increase with σ, thus attenuating the overall benefits of tensile stressing. Insight on the physical mechanisms responsible for these phenomena is obtained by measuring, at different stress levels, Wh versus temperature (20 °C≤T≤280 °C). Topological rearrangements of the domain structure and interaction of the Bloch walls with localized stress fluctuations are envisaged, in association with roughness of the ribbon surface, as the main sources of coercivity and losses. As to the relaxation aftereffect, this is shown to produce additional loss under fairly restricted conditions of temperature and magnetization rate.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4412-4414 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hysteresis, power losses, and the Barkhausen effect are investigated in an Fe-based highly magnetostrictive amorphous material, as a function of applied stress. By means of the static and dynamic Preisach model, and of existing theories of the Barkhausen effect, the results are shown to be compatible with the existence of a characteristic structural length δc, playing a role similar to that of grain size in crystalline materials. At low applied stresses, where the magnetization process is dominated by quenched-in stresses σi, δc is identified with the typical wavelength of σi fluctuations. The theoretical analysis leads to the estimate δc∼70–100 μm and 〈σi〉∼3.5 MPa. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4768-4770 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interplay between material microstructure and magnetic hysteresis is studied in rapidly quenched Si–Fe alloys. Two ribbons of different average grain dimension 〈s〉 (35 and 160 μm) were prepared by annealing at different temperatures and studied through two independent approaches: Barkhausen noise measurements, and Preisach analysis of static and dynamic hysteresis loops. In order to monitor the effect of demagnetizing fields on the magnetization process, the strips were progressively shortened from 30 to 10 cm. The correlation length of a domain-wall jump was estimated through the analysis of Barkhausen jump distributions versus apparent permeability. The correlation length of the coherent magnetization reversals controlling excess dynamic losses was estimated through the Preisach analysis of dynamic hysteresis loops. In the sample with lower 〈s〉, both the Barkhausen and the dynamic loss correlation lengths are comparable to 〈s〉, showing that a single structural feature governs all aspects of magnetization reversal. Conversely, in the high 〈s〉 sample, the ribbon thickness competes with 〈s〉 in controlling static and dynamic magnetization processes. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 133 (1994), S. 107-110 
    ISSN: 0304-8853
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 112 (1992), S. 272-274 
    ISSN: 0304-8853
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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