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  • 1
    Electronic Resource
    Electronic Resource
    Coaxial cable attenuation in NMR sample coil circuits (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 3242-3248 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An analysis is presented of the effect on power transfer and noise figure of attenuation in the radiofrequency coaxial cable (coax) between a NMR sample coil and the associated spectrometer. A matching network between the sample coil and the coax, which matches the coil to the coax characteristic impedance, is shown to decrease the noise temperature of the coax by a factor of the Q of the coil. In addition, the usual two-capacitor matching network, which provides a perfect match only if both capacitors are variable, is shown to yield an acceptably small mismatch over a wide range of frequencies even if one capacitor is fixed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140559
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  • 2
    Electronic Resource
    Electronic Resource
    Connections between magnetism and superconductivity in UBe13 doped with thorium or boron (invited) : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5782-5787 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetism and superconductivity appear to be intimately connected in the heavy electron (HE) superconductors. For example, it has been conjectured but not proven that the exchange of antiferromagnetic spin fluctuations are responsible for pairing in HE superconductors. In this paper we review recent results in U1−xThxBe13, where specific heat, lower critical field, and zero-field muon-spin-resonance (μSR) measurements reveal another second-order phase transition (below the superconducting transition) to a state which possesses small-moment magnetic correlations for 0.019≤x≤0.043. We present a new phase diagram for (U,Th)Be13 which indicates that the superconducting and magnetic order parameters are closely coupled. A discussion of the nature of the lower phase is presented, including the consideration of a possible magnetic (time-reversal-violating) superconducting state. When UBe13 is doped with B (UBe12.97B0.03) the Kondo temperature is decreased and the specific heat jump at the superconducting transition temperature is significantly enhanced. However, μSR measurements reveal no magnetic signature in UBe12.97B0.03, unlike the case for Th doping. The correlation between changes in the Kondo temperature and changes in the superconducting properties induced by B doping provide evidence for the importance of magnetic excitations in the superconducting pairing interaction in UBe13.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350160
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  • 3
    Electronic Resource
    Electronic Resource
    Normal-state 63Cu Knight shift and hole-band modification in Y1−xPrxBa2Cu3O7 (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5032-5034 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The 63Cu NMR Knight shift K has been measured in oriented powder samples of normal-state Y1−xPrxBa2Cu3O7, x=0.2 and 0.4. At plane Cu sites K is found to decrease with Pr doping, and a temperature dependence (dK/dT〉0) develops. The variation of K with bulk susceptibility χ is considerably greater than can be explained using RKKY coupling between Pr spins and Cu nuclei, and the temperature variation of K resembles that of χ in high-Tc systems with reduced conduction-hole concentration. These results are consistent with the view that Pr impurities significantly modify conduction-band properties, rather than acting as a "conventional'' pair-breaking mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344714
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  • 4
    Electronic Resource
    Electronic Resource
    Thermodynamics and magnetism in U1−xThxBe13−yBy : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5481-5483 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report specific heat and μSR measurements on Th (x =0.019) and/or B (y=0.03) substituted UBe13. The specific heat data show that either Th or B substitution reduces the Kondo temperature TK and increases the entropy at the superconducting transition by almost 20%, indicating an enhanced density of states. However, whereas μSR shows clear evidence for magnetic correlations for Th substitutions (0.019〈x〈0.043), no magnetism is observed for B substitutions. The enhanced specific heat jump in the B-substituted material is associated with a change in the superconducting properties as TK is reduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347972
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  • 5
    Electronic Resource
    Electronic Resource
    Pressure applied to epoxy-potted samples by thermal contraction of the epoxy matrix (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3642-3644 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Using a cuprous oxide manometer developed by Reyes et al. [Rev. Sci. Instrum. 63, 3120 (1992)] we have measured the pressure applied to powdered cuprous oxide due to thermal contraction of an epoxy matrix commonly used for cryogenic nuclear magnetic resonance experiments. The measured pressure is approximately 1 kbar at low temperatures, which is significant for certain materials. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147252
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  • 6
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance method for determining the magnetic easy direction in anisotropic paramagnetic powders (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 3038-3043 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a method for determining the magnetic easy direction (crystalline direction of maximum magnetic susceptibility) in powdered samples of paramagnetic crystals using nuclear magnetic resonance (NMR) spectroscopy. Single-crystal powder grains are aligned using a magnetic field both with and without rotation of the sample about an axis perpendicular to the alignment field. Depending on the magnetic easy direction of the material, only one method produces a good crystalline alignment. By qualitatively comparing the direction-dependent powder-pattern NMR spectra of samples aligned using the two alignment methods, we have successfully determined the magnetic easy directions in CePtSi and Y0.85U0.15Pd2Al3 compounds. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1488682
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  • 7
    Electronic Resource
    Electronic Resource
    Observation of high-temperature spin fluctuations in UBe13 by nuclear-spin relaxation (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3890-3892 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the extension of measurements of the 9Be spin-lattice relaxation rate in UBe13 from 300 up to 1000 K. They reflect the fluctuating local magnetic field at the site of the 9Be nuclei. Above about 100 K, there appears a new contribution in addition to the rate observed at lower temperatures. The high temperature contribution is modeled in terms of the thermal excitation of low-lying states of the U3+ ion along lines used by Felton et al. to explain their measurements of the specific heat. Our results indicate a splitting of 200±20 K between the ground and excited states of the system, and a lifetime of 8×10−14 s for the excited states (width =95 K).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340594
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature-dependent 27Al quadrupole splitting in YbCuAl (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3186-3188 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The quadrupole splitting of the 27Al NMR spectrum in the intermediate-valent (IV) compound YbCuAl has been measured as a function of temperature between 2 and 300 K. The splitting HQ between maxima of ±3/2(arrow-right-and-left)±1/2 powder-pattern satellites varies from (222±2) Oe at 10 K to (245±2) Oe above 80 K, in contrast to the nearly constant value (268±3) Oe observed in the nonmagnetic reference compound YCuAl over the same temperature range. Measurements at 4.2 K for applied magnetic fields between 2.3 and 8.2 kOe confirm that the splitting is strictly first-order quadrupolar in origin, i.e., that the temperature variation is not an artifact of the large 27Al magnetic line broadening in this system at low temperatures. The observed variation of HQ is two orders of magnitude larger than the corresponding anomalous lattice constant variation over approximately the same temperature range. This suggests considerable temperature dependence of the Yb elecronic structure, which is apparently an important contributor to the electric field gradient (EFG) at Al sites in YbCuAl. A similar temperature variation of the EFG at Yb sites has been attributed to crystal-line electric field (CEF) splitting of the Yb ionic states, but there is no indication of a CEF splitting in inelastic neutron scattering. The EFG therefore appears to reflect the breakup of the IV ground state with increasing temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338922
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  • 9
    Electronic Resource
    Electronic Resource
    The pseudo-brookite spin-glass system studied by means of muon spin relaxation (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4086-4088 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Zero-field muon spin relaxation (μSR) experiments have been performed on the spin glass Fe1.75Ti1.25O5. Above the spin-glass temperature of 44 K a distinct exponential μSR rate (λ) is observed, while below Tg a square-root exponential decay occurs, indicating fast spin fluctuations. Near 8 K, a maximum in λ is indicative of transverse spin ordering. The low λ values and the sharp λ peak at Tg are very promising for the study of spin freezing models like the Vogel–Fulcher law or the power law.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338536
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  • 10
    Electronic Resource
    Electronic Resource
    Ferromagnetism in reentrant Pd FeMn (abstract) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3491-3491 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Muon spin relaxation in zero applied field has been used to study the ferromagnetism of the reentrant ternary alloy [PdFe(0.35 at. %)] Mn(5 at. %). Below the ferromagnetic transition at Tc, the zero field linewidth due to quasistatically frozen impurities becomes much larger than expected from quasistatic ordering of the Fe spins only. This microscopic measurement shows that Mn spins participate in the quasistatic ferromagnetic ordering below Tc. The muon spin-lattice relaxation rate peaks at the Curie temperature Tc=8.25 K. Above Tc, the zero-field relaxation rate scales with earlier measurements of the ferromagnetic transition in PdMn (2 at. %) and shows the same behavior in a longitudinal applied field. We conclude that the Mn spins dominate the zero field dynamics of the ferromagnetic transition. The ferromagnet-spin glass transition at Tg can be identified from a peak in the imaginary part of the low-field ac susceptibility. The zero field muon spin-lattice relaxation rate is approximately constant for temperatures just above Tg.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335036
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