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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6150-6152 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5007-5009 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5771-5773 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5733-5735 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4995-4997 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5004-5006 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5016-5018 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6213-6215 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Materials with a large capacity to dissipate mechanical energy are of interest for passive vibration damping. We have measured the zero-field damping capacity of the giant magnetostrictive terbium–dysprosium–iron compounds by quasistatic stress–strain hysteresis loops. The magnetization and strain of the samples were measured for increasing and decreasing compressive stresses, up to 50 MPa. The zero-field, room temperature damping capacity (ΔW/W) was calculated from the stress–strain loops and is plotted against maximum stress. The damping capacity maximum for the alloy with the nominal Terfenol-D composition occurs at 4.1 MPa with the value 1.75 which corresponds to Q−1=0.28. The damping is almost independent of stress in a multi-phase sample, (Tb0.6Dy0.4)Fe1.4, which contains both Laves phase and elemental rare earth. © 1996 American Institute of Physics.
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