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  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of the amorphous-to-nanocrystalline transformation in Fe73.5Cu1Nb3Si13.5B9 (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3137-3143 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Isothermal measurements of the electrical resistance R were performed in samples of the alloy Fe73.5Cu1Nb3Si13.5B9 at temperatures where the nanocrystalline phase develops. At each temperature, nanocrystallization is associated to a very slow decrease of R(t) compared to conventional crystallization processes. X-ray-diffraction data were obtained on similar samples annealed at the same temperatures for selected times. The evolving nanocrystalline fraction turns out to be essentially proportional to the variation in the electrical resistance. The form of the kinetic law describing the R(t) decays is obtained by making use of a novel procedure, developed to analyze time-dependent properties characterized by a complex behavior. Nanocrystallization in the considered alloy appears as initially described by a Johnson–Mehl–Avrami kinetics with exponent n(approximately-equal-to)4, suggesting that the early stages of the process involve homogeneous nucleation and three-dimensional grain growth. For longer times, corresponding to the hearth of the nanocrystallization process, and at all temperatures, the functional form of the kinetic law drastically changes to a much slower power law of the type R∼At−α. The exponent α turns out to be essentially independent of temperature. Such a change presumably reflects a reduction in the grain growth velocity and/or in the nucleation rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354581
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of microstructure on thermal relaxation in nanocrystalline soft magnetic materials (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7463-7465 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interplay between activation volumes and microstructure is investigated in nanocrystalline Fe73.5Cu1Nb3Si13.5B9 (Finemet) alloys. Experiments are performed beyond the Curie point of the amorphous matrix, where relaxation effects are relevant. Measurements are analyzed within a theoretical framework where hysteresis and relaxation phenomena are jointly described. In highly crystallized samples magnetization processes are characterized by a unique length scale. In poorly crystallized samples the system behavior is controlled by a distribution of characteristic volumes related to structural disorder. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1355349
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  • 3
    Electronic Resource
    Electronic Resource
    dc Joule heating of amorphous metallic ribbons: Experimental aspects and model (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 1053-1060 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A dc technique of Joule heating has been developed with the purpose of developing unconventional crystallization products in amorphous metallic ribbons. The thermal effects of a continuous current flow on Fe40Ni40B20 and Fe80Si10B10 amorphous ribbon strips are examined. The evolution of the temperature in samples submitted to different values of electrical current is followed by measuring the variations in the electrical resistance of the ribbon strips. A model of sample heating is developed and shown to predict both the steady-state temperature of the ribbon strips and the law of approach to the steady state. A number of experimental data, obtained from multiple-thermocouple measurements, x-ray diffractometry, and differential scanning calorimetry, support the model's assumptions. The effect of fluctuations in the room-temperature resistance is discussed. The temperature behavior of samples submitted to free cooling after a Joule-heating treatment is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144177
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  • 4
    Electronic Resource
    Electronic Resource
    Power losses in thick steel laminations with hysteresis : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4575-4577 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.361873
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic properties and giant magnetoresistance in melt-spun Co-Cu alloys (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 392-397 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic, structural, and transport properties of as-quenched and annealed Co10Cu90 samples have been investigated using x-ray diffraction and a SQUID magnetometer. The largest value of MR change was observed for the as-quenched sample annealed at 450 °C for 30 min. The magnetic and transport properties closely correlate with the microstructure, mainly with Co magnetic particle size and its distribution. For thermal annealing the as-quenched samples below 600 °C, the Co particle diameters increase from 4.0 to 6.0 nm with a magnetoresistance (MR) drop from 33.0% to 5.0% at 10 K. Comparison with the theory indicates that the interfacial electron spin-dependent scattering mechanism correlates with GMR for Co particle diameters up to about 6.0 nm. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360613
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic properties and giant magnetoresistance of magnetic granular Co10Cu90 alloys obtained by direct-current joule heating (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5062-5066 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The direct-current (dc) joule heating technique was exploited to fabricate giant magnetoresistance (GMR) Co10Cu90 granular alloys. The Co cluster precipitation process was investigated by calorimetric and x-ray diffraction measurements. At T=10 K, the largest MR change of 25.0% has been observed for the melt-spun Co10Cu90 ribbon annealed at I=5 A. The magnetoresistance scales approximately as the inverse Co particle size. At room temperature, it was found that the dc joule-heated samples show relatively high GMR in comparison with furnace-annealed samples. Based on the phenomenological GMR model, we assumed that it is a consequence of smaller Co particles formed in dc joule-heated samples. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359735
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  • 7
    Electronic Resource
    Electronic Resource
    Relaxation of magnetoresistance and magnetization in granular Cu90Co10 obtained from rapidly quenched ribbons : The 6th joint magnetism and magnetic materials (MMM)−intermag conferenc (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6817-6819 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bulk granular Cu90Co10 systems displaying a negative giant magnetoresistance (GMR) were produced by submitting melt-spun ribbons to conventional annealing and dc joule heating in order to induce diverse microstructures. Room-temperature GMR values up to 9% at 20 kOe were found in samples produced using both kinds of thermal treatments. An evolution from a superparamagnetic towards a ferromagnetic behavior has been observed in samples submitted to different heat treatments. A long-time, nearly logarithmic relaxation of the magnetic remanence has been measured after fast removal of a magnetic field of 10 kOe. The progressive randomization of the magnetic moments also gives rise to a corresponding increase in the zero-field electrical resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358139
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  • 8
    Electronic Resource
    Electronic Resource
    Soft-hard magnetic composite wires obtained by a modified current annealing technique (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 5871-5873 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A current annealing procedure is proposed. Heat sinks were positioned along the sample, while annealing with current, inducing tailored temperature profile along its axis. Fe77.5Si7.5B15 amorphous wires were current annealed with this technique so that, magnetically soft and hard local regions develop. As a measure of this magnetic composite character, the coercivity profile was verified after annealing. Results are explained in terms of different power losses along the sample. Some possible applications as security labels of the annealed material are discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366456
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  • 9
    Electronic Resource
    Electronic Resource
    Hysteretic giant magneto impedance (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5814-5816 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Giant magneto impedance (GMI) has been measured in Fe77.5Si13.5B9 wires and Co67Fe3Cr3Si15B12 ribbons. The samples were annealed in order to induce specific anisotropies. An hysteretic behavior of the GMI is observed in both cases. Results show that this hysteretic behavior is related to irreversible changes in the magnetization processes of the samples. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368848
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  • 10
    Electronic Resource
    Electronic Resource
    Improved ductility of nanocrystalline Fe73.5Nb3Cu1Si13.5B9 obtained by direct-current joule heating (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2759-2761 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Direct-current joule heating is exploited to reduce the brittleness of ferromagnetic Fe73.5Nb3Cu1S13.5B9 nanocrystallized from the amorphous state. An ordering process occurring before nanocrystallization is singled out and shown to be responsible for sample embrittlement and magnetic-permeability degradation. The process is partially avoided by properly choosing the heating conditions. Nanocrystalline ribbon strips having substantially higher ductility than furnace-annealed samples, and maintaining excellent soft magnetic properties, are easily obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110326
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