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  • 1
    Electronic Resource
    Electronic Resource
    Study of weak magnetism effects in heavy-electron systems by μ+SR (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5639-5639 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We will present results from μ+SR investigations of the heavy-electron systems CeAl3, U2Zn17, UCu5, and UCd11. The latter three are known to order antiferromagnetically at low temperatures. The transition into the antiferromagnetic phase is clearly manifest in the μ+SR data, but also above the Néel temperatures some weak magnetism seems to persist as can be inferred from enhanced μ+ relaxation rates even in zero applied field. The involved effective moments are much reduced in comparison to the free-ion f moments, generally below 0.5 μB, and the magnetic order may be of the spin-glass or spin-density wave type. In nonmagnetic CeAl3 a spontaneous μ+ precession signal appears below 0.7 K in zero external field which implies the presence of even some coherent magnetic order of probably very short range in this system. These findings are consistent with other recent μ+SR and neutron scattering work, indicating that weak magnetic mechanisms seem to be a characteristic feature of heavy-electron systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342281
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Search for selectivity between optical isomers in reactions of polarised positive muons with alanines and octanols (1974)
    [s.l.] : Nature Publishing Group
    Nature 252 (1974), S. 692-694 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] One possible 'non-chance' explanation stems from the unequal decomposition of optical isomers5,6 and the appearance of optical activity in the products of light-mediated reactions7?10 in circularly polarised light. A slight excess of right-circularly polarised light in sunlight reflected and/or ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/252692a0
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  • 4
    Electronic Resource
    Electronic Resource
    Positive muons in bismuth: determination of their sites, detection of a large local lattice contraction and giant associated electric field gradients, evidence for short and long range diffusion (1988)
    Springer
    The European physical journal 71 (1988), S. 473-490 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using a high purity Bi single crystal the temperature and orientation dependence of the zero and transverse field muon spin relaxation rate has been studied in detail. The results imply that the μ+ occupies one of the two possible interstitial sites in the distorted rhombohedral crystal structure of Bi below 10 K and the other site above 80 K. At both sites the nearest neighbor Bi atoms are found to be shifted towards the μ+ by ≈10% of their nominal distance, implying a large local lattice contraction. In concomitance extremely strong electric field gradients are manifest at the nn Bi nuclei. An almost temperature independent reduced relaxation rate in the temperature range from 20 K to 60 K is interpreted in terms of short range diffusion along a limited chain of alternating types of sites. Above 100 K both long range and short range diffusion are indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313934
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  • 5
    Electronic Resource
    Electronic Resource
    Spin dynamics in CuGeO3 studied by muon spin rotation (1994)
    Springer
    The European physical journal 96 (1994), S. 223-226 
    Details
    ISSN: 1434-6036
    Keywords: 76.75 ; 75.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report a muon spin rotation (μSR) study of the magnetic properties of the Cu2+ quasi-one-dimensional CuGeO3 system and its lightly-doped derivative Cu0.97Zn0.03GeO3. Susceptibility measurements on CuGeO3 show a sudden change in the vicinity of 14 K that has been interpreted before as a magnetic transition to a spin-Peierls state. μSR shows no evidence of spin freezing below 14 K, implying that the transition is to a magnetic state with no static (random or ordered) electronic moments. A modest slowing down of the electronic spin dynamics is also identified at this temperature. Similarly, no evidence of a transition to a static magnetic state is found for Cu0.97Zn0.03GeO3 whose susceptibility shows hysteretic behaviour between zero-field and field cooled measurements at 4 K, previously ascribed to spinglass-like behaviour. Given the nature of the muon spin as a local magnetic probe, the present results necessitate a re-interpretation of the origin of the susceptibility anomaly observed in the doped system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313287
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  • 6
    Electronic Resource
    Electronic Resource
    Diamagnetism and muon Knight shift in semiconducting Bi1−x Sb x single crystals (1992)
    Springer
    The European physical journal 86 (1992), S. 367-374 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Knight shift of positive muons (μ+) implanted in semiconducting single crystals of Bi1−x Sb x (x=0.085, 0.14, 0.19) has been measured as a function of temperature and sample orientation. The Knight shift (KS) is generally negative and is found to scale with the negative total macroscopic susceptibility; the scaling is independent ofx but dependent on the orientation. One concludes that only the valence and conduction bands near theL-symmetry point in the Brillouin zone contribute to the μ+ Knight shift, most likely by the contact hyperfine interaction. Furthermore the valence bands and the conduction bands seem to be associated with the same hyperfine coupling constants. These conclusions are quite unexpected and call for a new theoretical approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323729
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  • 7
    Electronic Resource
    Electronic Resource
    μ + SR studies of UM2Al3, M=Ni, Pd (1992)
    Springer
    The European physical journal 86 (1992), S. 159-160 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Positive-muon spin rotation (μ + SR) measurements have been carried out in the new heavy-fermion superconductors UM2Al3, M=Ni and Pd. In UNi2Al3 the observedμ + frequencies in zero applied field indicate commensurate antiferromagnetic (AF) ordering of U moments ∼0.1μ B /U atom. These moments coexist with superconductivity and have the highest values observed in an AF heavy-fermion superconductor. The absence of well-defined frequencies in zero-fieldμ + SR in the AF state of UPd2Al3 suggests symmetricμ + stopping sites. In this systemμ + SR linewidths belowT c yield a preliminary value of ∼8000 Å for the London penetration depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313820
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  • 8
    Electronic Resource
    Electronic Resource
    Detailed investigation of the “DIP” structure in the μ+-relaxation rate in Nb (1984)
    Springer
    Hyperfine interactions 17 (1984), S. 177-182 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The depolarization rate of positive muons implanted in a number of nominally pure, cylindrical Nb single crystals (maximal 250 ppm Ta, 100 ppm N + O) was investigated at two temperatures, viz. 14.0 and 36.8 K, in a high transverse field of 7.5 kG with the stroboscopicμSR technique in order to study the nature of the “dip” at 22 K. To determine the sites at which the muon is trapped on both sides of this dip, the full angular dependence of the depolarization rate was measured by rotating a large single crystal around its 〈110〉 cylinder axis in a transverse magnetic field. The resulting curves for both temperatures are quite different, reflecting clearly the different environment in which the muon is trapped above and below 22 K. The trapping site at 36.8 K was identified to be of tetrahedral symmetry, located near a Ta substitutional impurity and possibly associated with an interstitial impurity. Lattice distortions due to these impurities and radial relaxation around the muon,δR/R, were determined. The latter is +6.7(6)% for nearest neighbors and −6(2)% for next nearest neighbors. The 14.0 K angular dependence could not be fitted by considering distorted tetrahedral and octahedral sites and pointlike muons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02065899
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  • 9
    Electronic Resource
    Electronic Resource
    Positive muons in antimony bismuth alloys (1984)
    Springer
    Hyperfine interactions 17 (1984), S. 387-391 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract StroboscopicμSR and TD-μSR techniques were used to measure theμ + Knight shiftK μ, and relaxation rateλ inSbBi alloys as functions of magnetic fieldH, temperatureT, the angleθ betweenH and the crystallineĉ axis, and the concentration [Bi] of alloyed Bi. In pure Sb and inSbBi (6.5%),K μ (θ=0) andK μ (θ=π/2) both decrease linearly withT up to about 100 K, but bothK μ and its anisotropy are smaller in the 6.5% alloy, indicating a “dilution” effect. With 15 at % Bi,K μ is reduced further but itsT-dependence and that ofλ are dramatically altered. At low temperaturesK μ (θ=0) inSbBi(15%) actually becomes negative and the sign of the anisotropy is reversed. In the same sample,λ is proportional toH at both 20 K and 150 K; at 120 Kλ is proportional toK μ ifθ is used as an implicit variable, but at 36 K this is not the case. A consistent phenomenological description is offered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02065931
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  • 10
    Electronic Resource
    Electronic Resource
    Possibility of a Lifshitz phase transition in Cd observed by a singularity in the muon Knight shift (1984)
    Springer
    Hyperfine interactions 17 (1984), S. 359-363 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract During the past much effort has been devoted to a systematic study of the muon Knight shiftK μ in metallic environments and its implications on the local electronic structure of hydrogen in metals [1]. These measurements in simple metals were essentially all carried out in polycrystalline samples at room temperature. The present measurements in Cd in polycrystalline and single crystal samples cover a temperature range between 20 K and the melting point of this strongly anisotropic metal (hcp crystal structure,c/a ratio 1.89 — idealc/a ratio 1.63). These measurements add qualitatively new and interesting aspects and insights on the screening of a light hydrogen isotope in a metal as well as on certain properties of the host material itself. The outstanding features of the muon Knight shift in Cd are: (i) a strong intrinsic temperature dependence with an increase ofK μ of more than 100% between 20 K and the melting point (T=593 K), (ii) an anomaly at 110 K in the form of a singularity in the isotropic part ofK μ which is interpreted as a band structure effect, (iii) an anisotropic Knight shift contribution fitting the expressionK(T,θ)=K iso(T)+K ax(T) * (3 · cos2 θ−1)/2, where both, the isotropic and the axial contribution ofK μ, are strongly temperature dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02065926
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