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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6150-6152 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The elastic moduli of the highly magnetostrictive TbxDy1−x alloys (x=0.5, 0.6, and 0.67) were measured at 77 K under conditions of constant magnetic field and constant magnetic induction. From these values the magnetic contribution to the moduli (intrinsic ΔE effect) and magnetoelastic coupling factor k were calculated. For Young's moduli measured under constant flux density (magnetically blocked conditions), it was found that EB∼20 to 50 GPa. For measurements made while maintaining a constant magnetic field (magnetically free conditions), it was found that Young's moduli EH minima range from ∼3 to 5 GPa. Such large differences between EB and EH yield magnetoelastic coupling factors in excess of 0.9. Theoretical expressions of the magnetic contribution to the elastic compliance, (1/EH−1/EB), were derived using the single vector magnetization rotation model.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4668-4670 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The magnetoresistance of transverse-field-annealed Metglas 2605SC (Fe81B13.5Si3.5C2) ribbons has been measured as a function of both applied field and imposed strain. A maximum magnetoresistance of 0.3%, obtained with applied magnetic field agrees with previous measurements of unannealed samples. The magnetoresistance changes with imposed strain are slightly smaller, and indicate the presence of inhomogeneities in the sample or the imposed strain.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5007-5009 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: It is now possible to achieve substantial magnetomechanical transduction in modified Bridgman-grown samples of Tb0.3Dy0.7Fe1.9 (Terfenol-D) which are grain-oriented to achieve nearly complete [112] alignment. Large magnetic-field excursions can be converted into large fractional dimension changes (ΔL/L〉10−3). In this paper measurements are reported of the average magnetomechanical coupling factor determined by (i) large field drives (〉1000 Oe) and (ii) large pressure changes (〉 20 MPa). By extending the small-signal magnetomechanical expressions to difference relationships Δε=sH Δσ+d ΔH and ΔB=d*Δσ+μσ ΔH, it is possible to determine large-signal coupling factors by k2=1−με/μσ, and (2) k2=1−sB/sH. Here με and μσ are the average magnetic permeabilities (ΔB/ΔH) at constant strain ε, and at constant stress σ, and sB and sH are the large signal elastic compliances (Δε/Δσ) at constant induction B, and constant field H. The square of the coupling factor is defined by k2=1−dd*/sHμσ. Using an apparatus which was designed to minimize demagnetizing effects, με, μσ, sB, sH, d, and d* were measured in large Bridgman-grown samples (10 cm×3.75 cm diam) for compressive stresses up to 49.1 MPa with field excursions from ±250 to ±750 Oe and pressure excursions from ±3.7 to ±19.0 MPa.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The magnetization and small signal alternating-current permeabilities of transverse-field-annealed amorphous magnetostrictive wires (Fe77.5B15Si7.5) with a fixed twist of 400 deg/m were examined as a function of applied axial tensile stress and axial direct-current (dc) currents. We observe multiple-featured magnetization curves which we attribute to the inverse Wiedemann effect, as well as a near total suppression of the large Barkhausen jumps when a dc current is flowing through the wire. Several properties of the wire depend on stress and would be useful for sensor applications; figures of merit of 1700–2600 for torque sensors were obtained.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5771-5773 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: From magnetization (M) and magnetostriction (λ) measurements as a function of magnetic field and stress, the temperatures of anisotropy compensation, Tm, for technologically important TbxDy1−x(Fe1−yTy)1.9 [T=Co,Mn (0.3≤x≤0.5) (0≤y≤0.3)] were determined. Measurements of M and λ encompassing Tm were made under compressive stresses from 8.8 to 36 MPa and for temperatures from −196 to +130 °C. In agreement with earlier measurements, Tm decreases with increasing Tb. Substitution of Mn for Fe for fixed x also decreases Tm. In contrast with these observations is the increase of the anisotropy compensation temperature with the replacement of Fe by small amounts of Co. In the cases of both (1) increasing Tb content and (2) increasing Co content, the Curie temperature TC increases, yielding, in general, a higher magnetic moment and saturation magnetostriction of these alloys. Thus, compensation at a given temperature may be obtained in an improved class of Laves phase compounds, R(1)xR(2)1−x(Fe1−yCoy)2, where rare earths R(1) and R(2) are, for example, Tb and Dy.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2131-2133 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Si delta-doped layers of GaAs were grown by low pressure metal organic vapor phase epitaxy (LP-MOVPE). The results showed that, in LP-MOVPE, growth rate plays a crucial role in confinement of dopants and growth temperature has only a secondary effect. Effects of purge time, doping temperature, and doping period on sheet carrier concentration of delta-doped layers were studied. The effect of growth rate on confinement of dopants was discussed.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5733-5735 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The nitrogenation process of the TbFe3 intermetallic compound was studied by heat treating the alloy between 573 and 873 K in a nitrogen atmosphere. The structural and magnetic properties of the nitrogenated samples were characterized by x-ray diffraction (XRD), Mössbauer spectroscopy, and magnetic measurements. The magnetic moments of the nitrogenated samples were found to be a function of the annealing temperature and showed a minimum for the sample heat treated at 673 K. The XRD pattern of this sample (673 K) showed that the Bragg peaks of the 1-3 phase had completely disappeared and were replaced by a broad maximum indicating a breakdown of the TbFe3 structure into an amorphous phase. The room-temperature Mössbauer spectrum of the same sample consisted almost entirely of a quadrupole-split doublet plus a small amount of α-Fe and TbFe3. This doublet split into a broad spectrum upon cooling which is typical of amorphous rare-earth–transition-metal compounds. For samples heat treated at higher temperatures, the amount of α-Fe and TbN phases gradually increased. This nitrogenation process is unlike that of R2Fe17. In this study, nitrogen atoms do not go into the interstitial sites. Instead, they create a ferromagnetic (TC≈215 K) amorphous phase of Tb, Fe, and N which is stable over a wide temperature range.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4995-4997 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Gd has been added to binary alloys of Tb and Dy in order to raise the magnetic transition temperature and zero-anisotropy temperature of the alloys. Magnetostriction and differential-scanning-calorimetry measurements were made on four samples of the alloy system (TbxDy1−x)80Gd20 over temperatures from 50 to 300 K in applied fields of 6–20 kOe. The two lowest-order basal-plane magnetostriction constants were derived from the data, as was the basal-plane anisotropy constant. The addition of 20% Gd was found to increase the magnetic transition temperatures, but to decrease or eliminate the zero-anisotropy temperature.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5004-5006 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The longitudinal magnetostriction (Δl/l) for twinned TbxDy1−xFe1.95 material, prepared by the free-standing float-zone method, has been previously measured and found to be very large (2000×10−6) at room temperature. The magnetostrictions for the [111] and [11¯0] crystallographic axes perpendicular to the applied stress and magnetic-field [112¯] direction are presented as functions of temperature, applied stress, and applied magnetic field. The temperature range is ±60 °C centered about the anisotropy compensation temperature of Terfenol-D (+10 °C). The stress ranges from 2 to 32 MPa and the magnetic field to ±2000 Oe. The temperature dependence of the perpendicular axes magnetostriction is similar to that of the conventional magnetostriction measured parallel to the [112¯] growth axis. Relative values for the saturation magnetostriction exhibit a large anisotropy in the perpendicular direction, ranging from −117% for the [111] to +19% for the [11¯0] direction. This ratio stays constant as a function of temperature above the compensation temperature for a given prestress above 8 MPa. The largest absolute value of magnetostriction (2260×10−6) occurs in the [111] direction at 10 °C at a prestress pressure of 12 MPa. Above this temperature the magnetostriction falls at a rate of −8.5×10−6/°C. The volume magnetostriction is shown to be small and highly sample dependent. All data is consistent with the parent-twin magnetization model and also the magnetostriction values along nonprincipal axes.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5016-5018 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Terfenol (Tb0.3Dy0.7Fe1.9) and related materials have proven useful as electromechanical transducers. As with other transducers, these materials exhibit hysteresis, which must be included in any model of the transducer. Preisach theory is one of the available models that includes the effects of hysteresis. The theory is able to include the hysteresis by maintaining a history of the field reversals in the material. Both the strain and magnetization hysteresis loops in a 3.8-cm-diam Terfenol rod have been measured under 20.7-MPa longitudinal stress. The data has been used to derive a Preisach model of the rod, including hysteresis effects. It is possible to predict the strain and magnetization of the rod, including minor loops, with about 10%–15% accuracy.
    Materialart: Digitale Medien
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