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  • Articles: DFG German National Licenses  (30)
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  • Articles: DFG German National Licenses  (30)
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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rare-earth–iron alloys, R0.9Fe0.1, R0.72Fe0.28, and R0.42Fe0.58 (R=Tb0.6Dy0.4), containing the R/RFe2 eutectic composition were prepared by Bridgman and free-standing zone-melting techniques. Magnetization measurements were made in fields up to 800 kA/m between 55 and 300 K. A huge increase in magnetization below 210 K occurs as the R component becomes ordered. At low applied magnetic fields there is clear identification of both the ferromagnetic ordering temperature TC and the Néel spiral ordering temperature TN of R. (For Tb0.6Dy0.4, TC=165 K, TN=210 K.) Magnetization and magnetostriction measurements reveal very large magnetocrystalline anisotropies for both the R and the RFe2 components. Unexpectedly, at 77 K, were the rare-earth component of the eutectic system is ordered and the magnetostriction is large (λhγ(approximately-greater-than)0.6%), the magnetostriction is largest in the samples containing the largest amount of the RFe2 phase. Young's modulus measurements reveal the reduction in the stiffness with the addition of the softer rare earth to the stiff RFe2 compound.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have examined the effects of magnetic viscosity (magnetic aftereffect) on the giant magnetoresistance (GMR) of NiO/Permalloy(45 Å)/Cu(45 Å)/Permalloy(45 Å) exchange-biased spin-valve structures grown by direct current (dc) magnetron sputtering on Si substrates. One of the samples had a 6 Å Co layer on both sides of the Cu layer. GMR is a sensitive indicator of magnetic viscosity effects since any time dependence in the magnetization reversal of one of the layers is reflected directly in the GMR. Two different types of GMR measurements were made over the temperature range of −30 °C to 50 °C. The maximum time for the resistance to stabilize to 1 part in 104 ranged from about 70 to 200 s for both samples at the temperatures studied. The time dependency of the GMR was well described by C+S ln t, where S and C are constants; S is called the coefficient of magnetic viscosity. This equation characterizes the classic time dependent behavior of the magnetization. The maximum magnitude of S was found to decrease as the temperature was increased.
    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 79 (1996), S. 6216-6218 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of Young's modulus has been measured for a series of Tb1−xDyxZn pseudobinary compounds with x ranging from 0 to 1. From the sharp dips in the modulus vs temperature data, the reorientation transition temperatures have been determined, and the magnetic phase diagram deduced. Magnetization measurements taken on the same samples show less pronounced features at the corresponding temperatures. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently it was discovered that composites of Terfenol-D alloys with an insulating binder produce very large magnetostrictions. Resistivities of these composites reach high values, making them attractive for high-frequency applications which require small eddy current losses. In this paper the magnetostriction, magnetization, and Young's moduli measurements made under constant magnetic field conditions and under constant flux conditions are reported. From these measurements, magnetomechanical coupling factors are calculated. The properties are compared to those of ordinary metallic Terfenol-D and nickel. Two different types of composites were investigated. In the first type the composite has an isotropic structure and in the second type, anisotropic. It is shown that the anisotropic type is more desirable since it possesses both higher magnetostriction and higher coupling factors. It is also clearly shown that the magnetization process for the anisotropic type can be explained by a 180° domain wall motion followed by a magnetization rotation.
    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 61 (1987), S. 3803-3803 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new technique for measuring strain with extremely high resolution was developed. This technique relies on the ultrasensitive (high coupling factor) amorphous ribbons prepared by magnetic field annealing.Here certain ribbons (e.g., Metglas 2605SC, 2605S-2) when annealed in a transverse field achieve magnetomechanical coupling factors k33≈0.95.1 In this technique the sensitive ribbon is bonded in place on an aluminum bending member with a highly viscous liquid (η≈107 cP at 298 K). This procedure allows the ribbon to remain in a stress-free environment following an initial relaxation period of approximately 10 min. In this state the ribbon is in a "blocked'' (constant strain) condition while at the same time being stress-free. Since the susceptibility of the ribbon is highly strain dependent, a measurement of the susceptibility is a direct measurement of the strain. We define a figure of merit (FM) as (∂χ/∂ε)/χ in analogy with (∂R/∂ε)/R for a conventional strain gage. Values of FM of about 2×105 were obtained. This is three orders of magnitude better than semiconductor strain gages. The main features of this technique are its large dynamic range, high sensitivity and strain resolution, very small temperature dependence, and broad frequency range. In a simple device, we measured strains as low as 3×10−10 and secured a dynamic range of 104. The potential dynamic range exceeds 105. Measurements of FM and dynamic range were made from 0.01 to 1 Hz. We expect no deterioration in operational characteristics far above 1 Hz. Calculations also indicate only a slight temperature dependence of the FM from 0 to 500 K.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6250-6252 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization, magnetostriction, and elastic modulus measurements were made on single crystal specimens of Tb1−xDyxZn. Easy axis magnetization rotation as much as 26° were observed in the (001) plane of Tb0.75Dy0.25Zn below 33 K. From these measurements, values of the K4/K8 anisotropy ratios were calculated. No easy axis magnetization rotation was observed in the x=0.6 and x=0.8 single crystals. Magnetostriction and modulus measurements at 77 K in Tb0.4Dy0.6Zn showed a saturation magnetostriction of ∼5×10−3 and a maximum magnetomechanical coupling factor of 0.96. © 1999 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5405-5407 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the magnetomechanical coupling in amorphous 2605SC ribbons which have been coated by magnetron sputtering on one or both sides with copper films between 31 and 186 nm in thickness. Coating on one side produces an additional resonance mode which may be a coupling of an extensional and flexural mode. Coating on both sides greatly increases the anisotropy and reduces the coupling factor. Analysis indicates that these effects are due to stresses imposed by the coating on the ribbon and can be ameliorated by control of deposition parameters. In transverse-field annealed amorphous Fe77.5B15Si7.5 wire material we find a lower coercive force and lower values of applied fields required for saturation than in our ribbon investigations. This is probably due to a lower surface-to-volume ratio for the amorphous wire, i.e., surface defects play a lesser role in the wire geometry. We find a different magnetization process. Values of magnetomechanical coupling approach ribbon values. Saturation values of magnetostriction are equivalent. Values of the transverse anisotropy in the wire material are lower than what we have previously obtained in our ribbon material. We conclude that the amorphous wire will be a good sensor material.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6253-6255 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization and magnetostriction of a variety of 3/16-in.-diam Laves phase rods of TbxDyyHo1−x−yFe1.95 grown in the form of [112] oriented dendritic compounds were measured as a function of applied magnetic field −3000〈H〈3000 Oe and compressive stresses of 22 and 47 MPa at room temperature. Compared to Terfenol-D (Tb0.3Dy0.7Fe1.95), the widely used room temperature magnetostrictive material, Ho containing alloys can have substantially lower hysteresis with only slightly lower magnetostriction. The Ho concentration was kept relatively small (≤0.3) to avoid a substantial decrease in the magnetostriction, while the ratio of x and y was chosen to examine alloys spanning the line of minimum magnetic anisotropy. Most of the compositions have twice the Ho content of the previous study. As expected, alloys with higher Ho concentrations showed narrower hysteresis curves. The data shows that at 22 MPa, the Tb0.28Dy0.57Ho0.15Fe1.95 composition has a minimal (3%) loss of magnetostriction, while the hysteresis width decreased by 15%. Between 15% and 20% Ho content, the magnetostriction drops abruptly. For alloys with a fixed Ho concentration, the strain showed a peak near the expected anisotropy minimum, but the hysteresis width always increased with increasing Tb content. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3644-3646 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mössbauer effect measurements were obtained on smooth-surface Fe78B13Si9 amorphous ribbons annealed in a transverse magnetic field at high temperature. Absorption spectra were obtained with the ribbon plane tilted at several angles with respect to the direction of the γ rays, in an external field ranging from 0 to 10 Oe. Intensity ratios were analyzed to obtain the magnetization as a function of field. A large zero-field spread was deduced and excess scatter near the anisotropy field was observed.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5786-5788 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization and magnetostriction of a variety of Laves phase rods of TbxDyyHo1−x−yFe1.95 grown in the form of [112] oriented dendritic platelets were measured as a function of magnetic field H(−2200〈H〈2200 Oe), compressive stress (20, 30, and 40 MPa), and temperature T(−60〈T〈80 °C). Compared to Terfenol-D (Tb0.3Dy0.7Fe1.95), Ho containing alloys can have lower hysteresis with only slightly lower magnetostriction. Sample compositions were chosen both along a line of minimum near room-temperature anisotropy (Tb0.3Dy0.7Fe1.95–Tb0.20Dy0.22Ho0.58Fe1.95) and at Ho0.15 and Ho0.30 across the line. © 2000 American Institute of Physics.
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