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  • 1
    Electronic Resource
    Electronic Resource
    Raman scattering study of antimony-based skutterudites (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2622-2626 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectra of single-crystal CoSb3 and RhSb3 and of polycrystalline IrSb3 have been studied. We have also studied four different polycrystalline-filled skutterudite samples, Ir4LaGe3Sb9, Ir4NdGe3Sb9, Ir4SmGe3Sb9, and Fe4CeSb12, where rare-earth ions occupy the voids in the skutterudite structure. These void-filling ions interact with some of the lattice vibrations in this structure and produce a shift and broadening of the observed lines. The most prominent lines in all of the samples are the Sb4 ring-breathing modes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361132
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  • 2
    Electronic Resource
    Electronic Resource
    Study of desorbed hydrogen-decrepitated anisotropic Nd-Fe-B powder using x-ray diffraction : The 6th joint magnetism and magnetic materials (MMM)−intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6259-6261 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The intrinsic magnetic coercivity (Hci) of Nd-Fe-B-based permanent magnet material is profoundly affected by hydrogen absorbed during the hydrogen decrepitation (HD) process for producing anisotropic powders from bulk anisotropic hot-deformed MAGNEQUENCH (MQ) magnets. Hydrogen (H) content and x-ray diffraction measurements clarify the effects of H and desorption temperature (Td) on the intrinsic magnetic anisotropy (IMA) of the Nd2Fe14B-type phase and the nature of the intergranular phases, both of which are crucial for high Hci. The Nd-rich intergranular phase disproportionates during HD, initially forming a microcrystalline Nd-hydride phase, possibly Nd2H5. For Td≤220 °C, H remains in the Nd2Fe14B-type phase, severely degrading the IMA, which causes a low Hci. For 220 °C≤Td≤250 °C, enough H desorbs from the Nd2Fe14B-type phase and the IMA recovers its large prehydrided value, and the microstructure supports a high Hci≤10 kOe in spite of the H disproportionated intergranular phase. Only for Td(approximately-greater-than)250 °C is Hci degraded by the microstructure, corresponding to further H desorption and the microcrystalline Nd-hydride phase becoming well-crystallized NdH2. The NdH2 phase decomposes with continued H desorption and at Td(approximately-greater-than)580 °C recombines to re-form the Nd-rich intergranular phase of prehydrided MQ material. H is completely desorbed above 580 °C and Hci(approximately-greater-than)11 kOe, nearly that of the prehydrided MQ magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358298
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  • 3
    Electronic Resource
    Electronic Resource
    Neutron irradiation study of Nd-Fe-B permanent magnets made from melt-spun ribbons (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5305-5307 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Radiation-induced changes in the magnetization of sintered Nd-Fe-B permanent magnets are known to vary widely among specimens produced by different manufacturers. Samples of Nd-Fe-B MAGNEQUENCH magnets, which are made from melt-spun ribbons, have not been studied and show a much reduced sensitivity to neutron irradiation than do sintered Nd-Fe-B magnets. All melt-spun ribbon-based MAGNEQUENCH magnets, i.e., epoxy-bonded, hot-pressed, and die-upset magnets, show essentially the same slow decrease in magnetic remanence with neutron dose. Measurements of the open-circuit remanence Br/Br 0 at various times during the irradiation show a decay of only 1.5% of the preirradiated value for the MAGNEQUENCH magnets after 1 h of irradiation, or a dose of 1.4×1016 neutrons/cm2, compared to a 4.6% drop in remanence for the best sintered Nd-Fe-B magnet (Sumitomo 30H) with the same irradiation dose. Moreover, after 5.3 h of irradiation, the remanence drops by only 3% for the MAGNEQUENCH magnets. Magnets made from melt-spun ribbons are thus the least sensitive to neutron irradiation so far measured for Nd-Fe-B permanent magnets, but are somewhat more sensitive than samarium-cobalt magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342400
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic and structural studies of erbium-iron-manganese-boron alloy (invited) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3119-3123 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of neutron diffraction and magnetization measurements on powder samples of Er2(Fe,Mn)14B. We find that the unit cell expands with increased concentration of manganese as larger manganese atoms replace the smaller iron atoms within the transition metal sublattice. The preferential occupancy of transition metal sites is also affected since manganese prefers positions with larger site volumes, such as the j2, while iron prefers smaller site volumes, such as the k2. At low temperatures (4.2 K) the simple collinear moment model of the magnetic structure, valid at higher temperatures, is not sufficient to explain the existence of reflections forbidden in the space group P42/mnm. A five-sublattice model is used in which each of the two rare-earth sites splits into two distinct sublattices whose moments are oppositely canted from the direction antiparallel to the transition metal moment. The linear field dependence of the magnetization provides support for this moment configuration. Neutron diffraction analysis of the transition metal moments is compared to the compositional dependence of the magnetization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340863
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  • 5
    Electronic Resource
    Electronic Resource
    Moment canting in the erbium-iron-manganese-boron system: Magnetization effects (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3562-3564 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report that Er2Fe14−x MnxB compounds at 4 K have a component of the magnetization which is linear in the applied field. We attribute this to a noncollinear Er moment structure in which the Er moments rotate under application of an external field. The slope becomes very large (dM/dH=0.51μB/f.u./T) at x=2, near the composition where the net Er and transition metal sublattice magnetizations are equal at zero temperature. This enhanced field dependence suggests an additional moment rotation mechanism near compensation. In the compositions x=2.5 and 2.75, just above zero temperature compensation, the slope of the linear field dependence abruptly increases when the field reaches 5 and 7.2 T, respectively. High Mn concentrations have rare-earth-dominated magnetization curves with substantial curvature at low fields and a linear nonsaturating field dependence at high fields. Anomalies are also observed in the initial magnetization behavior above x=2.5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338726
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of manganese substitution in erbium-iron-manganese-boron: Spin reorientation, moment compensation, and structure (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2314-2317 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The importance of the Nd2Fe14B tetragonal phase to permanent magnet technology has led to the study of systems with rare-earth and transition-metal substitutions. We report on alloys formed by replacing iron with manganese in the Er2Fe14B system. Samples were characterized by x-ray diffraction, thermal analysis, and magnetization measurements. The 2-14-1 tetragonal lattice type forms for a large fraction of manganese substitution but not the entire range. The Curie temperature decreases rapidly from 560 K for Er2Fe14B to 20 K for alloys with high concentrations of manganese. The spin reorientation temperature also decreases, but not as rapidly. Compensation points were observed in the temperature dependence of the magnetization for intermediate manganese concentrations. The rapid decrease in the magnetization with Mn substitution indicates that, in addition to replacing a Fe moment, Mn lowers the average moment of the remaining Fe atoms. The linear response of the magnetization to the applied field arises from a noncollinear moment structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337942
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  • 7
    Electronic Resource
    Electronic Resource
    Critical-current measurements of high-Tc superconductors using a transformer technique (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5518-5522 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report transport critical-current measurements of the YBa2Cu3Oy high-Tc superconductors using a contactless transformer technique. A critical-current density of 15.9±1.0 A/cm was observed at 77 K for samples fabricated by a standard preparation method for the high-Tc superconductors. The addition of a small amount of silver to samples of YBa2Cu3Oy has a dramatic degrading effect on the critical current. This is in sharp contrast to the Meissner-effect results, where silver addition has a minimal effect. No significant systematic frequency dependence of the critical-current determination was found between 10 and 5000 Hz. Visual observations of "blips'' in oscilloscope traces and an extrapolation of signals to zero blip height gave consistent results and established an uncertainty of ∼3% for critical-current determination. The range of dimensions of the ring-shaped samples yielded an uncertainty of ∼3% for the cross-sectional area. The overall uncertainty for an absolute measurement of the critical-current density is consequently ∼6%. The uncertainty in relative measurements of the critical-current density is very much less.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343705
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature-dependent magnetization of canted moments in erbium- iron-manganese-boron (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2783-2785 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization as a function of field up to 9 T is reported for Er2Fe14−xMnxB compounds with x=2 and 2.5 at temperatures T between 4 and 120 K. The noncollinear basal plane moment structure which exists among the Er and transition-metal moments within this temperature regime gives rise to an unusual nonsaturating field-dependent magnetization behavior. The magnetization increases linearly with field up to a field H*, where the slope dM/dH abruptly changes. M(H) is again linear above H*, but with a much steeper slope dM/dH∼0.5 μB/formula unit/T. H* increases monotonically with temperature for x=2, until no slope change is observed at experimentally accessible fields when T=120 K. In the x=2.5 sample, H* initially decreases with increasing temperature, and reaches a minimum at 55 K. This behavior appears in a plot of M(T) as a compensation temperature Tcomp, that is, as a minimum in the magnetization near 55 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341577
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  • 9
    Electronic Resource
    Electronic Resource
    Coherent-state Hall effect in the heavy fermions CeCu6 and U2PtC2 (abstract) (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4397-4397 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Hall effect is found to set the scale for coherence in the normal state of CeCu6 and U2PtC2. CeCu6 is a nonmagnetic, nonsuperconducting heavy fermion system.1–4 Its resistivity at high temperature is like that of a collection of incoherent Kondo scatterers. At low temperature the resistivity smoothly decreases to a very small value, indicating that scattering has become coherent. The Hall effect has two strong extrema in its temperature dependence which define a high-temperature incoherent scattering region, a transition region, and a low temperature coherent region. Although U2PtC2 is superconducting below 1.5 K,5 the Hall results in the normal state show two extrema similar to those of CeCu6. However, these features are scaled to higher temperatures, consistent with the smaller low-temperature electronic specific heat and higher Fermi temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338435
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  • 10
    Electronic Resource
    Electronic Resource
    Hydrogen decrepitated anisotropic Nd-Fe-B powder: Hydrogen desorption and magnetic properties : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6482-6484 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hydrogen decrepitation (HD) process easily pulverizes rapidly solidified, hot-deformed Nd-Fe-B (MQ3) magnets but degrades the magnetic properties. Recovery of high-performance magnetism in HD MQ3 powder has always required hydrogen desorption at temperatures above 600 °C. It is reported that desorption at the relatively low temperature of 240 °C restores magnetic coercivity Hci to above 10 kOe despite residual hydrogen in the material. Desorption between 240 and 580 °C significantly degrades Hci but not the intrinsic magnetic anisotropy. Hydrogen is reabsorbed when the desorbed powder is cooled from above 600 °C to room temperature in the presence of small amounts of residual hydrogen gas. This hydrogen reabsorption strongly degrades the coercivity but does not affect the intrinsic magnetic anisotropy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352587
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