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  • 1
    Electronic Resource
    Electronic Resource
    Observation of the morphology of thin films of solid helium deposited from the fluid onto sapphire (1985)
    Springer
    Journal of low temperature physics 58 (1985), S. 153-170 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Thin layers of solid helium were grown on sapphire single-crystal substrates at pressures from about 500 bar to 9 kbar. Grain boundaries can be observed in these layer crystals. The morphology of the grains depends on the crystal modification. In the hcp phase (below about 1.13 kbar) a system of parallel bands is observed, probably due to slip and twinning. In the fcc phase (above 1.13 kbar) a polygonal structure similar to a helium froth is found. Melting of this froth in the fcc phase shows grain boundary melting; fluid helium is wetting the fcc grains. Grain boundaries in the hcp phase are, in contrast, not wetted by fluid helium. Near the triple point at 1.13 kbar and 15.0 K one can deposit both crystalline phases side by side. In such structures, the transition fcc → hcp4He can be observed during isothermal holding. The transition proceeds by the parallel motion of low-energy grain boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682571
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  • 2
    Electronic Resource
    Electronic Resource
    Messung der kritischen Übersättigung von Dämpfen mit der Diffusionsnebelkammer (1956)
    Springer
    The European physical journal 143 (1956), S. 559-590 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Zusammenfassung Bei einer spezieil für das Studium von übersättigten Dämpfen konstruierten Diffusionsnebelkammer wird der Temperaturgradient zwischen der unteren geheizten und der oberen gekühlten Fläche so eingestellt, daß bei eingeschaltetem elektrischen Feld neben den an Ionen in Teilchenbahnen gebildeten Tröpfchen gerade die ersten durch statistische Schwankungen spontan entstehenden Tröpfchen auftreten. Durch die Berechnung der Temperatur- und Dampf-Partialdruckverteilung in der Kammer kann aus den gefundenen Einsatzpunkten der Tröpfchenkondensation mittels einer Enveloppenkonstruktion die kritische Übersättigung in Abwesenheit von Ionen gefunden werden. Es wurden Methyl- und Äthylalkohol untersucht. Die gefundenen kritischen Übersättigungen stimmen innerhalb einiger Prozente mit der von der Theorie vonBecker undDöring gegebenen Vorhersage überein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01333567
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  • 3
    Electronic Resource
    Electronic Resource
    The copper isotope effect in oxygen-deficient YBa2Cu3O7−δ (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 591-594 
    Details
    ISSN: 1572-9605
    Keywords: Isotope effect ; electron-phonon interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The copper isotope effect (63Cu —65Cu) was investigated for oxygen-deficient YBa2Cu3O7−δ with transition temperatures between 40 and 91 K. The isotope exponent αCu=−ΔℓnTc/ΔℓnmCu is negative for all transition temperatures. It is small, αCu≈−0.14, in the 60 K plateau, and unobservable for Tc=91 K. In regions away from these special conditions, αCu reaches large values of up to αCu=−0.4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727433
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  • 4
    Electronic Resource
    Electronic Resource
    Isotope Studies of the CMR Compounds La1−xCaxMnO3+δ (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 263-267 
    Details
    ISSN: 1572-9605
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Oxygen isotope effect studies of the ferromagnetic Curie temperature T c of La1−x Ca x MnO3 are presented. The isotope exponent α0=−ΔlnT c/Δlnm 0 changes from 0.4 to 0.14 in the range 0.2〈x〈0.43. The isotope exponent decreases strongly with increasing tolerance factor, or decreasing lattice distortion. Above Tc the conductivity is characteristic of small polarons. Raman scattering shows a prominent peak at 230 cm−1. The peak width could be related to site-dependent Jahn–Teller distortions above T c, becoming significantly smaller at and below T c. IR reflectivity data show a much larger zero frequency IR conductivity than dc conductivity. The IR peaks are independent of temperature between 150 and 295 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007764223904
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  • 5
    Electronic Resource
    Electronic Resource
    Comment on the minimum temperature hysteresis observed for the HCP-FCC4He transition (1981)
    Springer
    Journal of low temperature physics 45 (1981), S. 91-95 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown that the minimum temperature hysteresis of 30 mK, observed for the hcp-fcc4He transition near the triple point with the fluid, is a consequence of the adiabatic character of this transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00661144
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrasonic attenuation in hcp 4He (1978)
    Springer
    Journal of low temperature physics 30 (1978), S. 579-592 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: The ultrasonic attenuation was measured for longitudinal sound waves in solid hcp 4He at frequencies of 5, 15, and 25 MHz from 0.25 to 3.5 K. Near melting, the attenuation is very small and in agreement with theoretical predictions. In most samples the attenuation rises gradually with falling temperature until a point is reached which approximately corresponds to the onset of a previously observed velocity anomaly. Then the attenuation rises more quickly and remains very large to the lowest temperatures measured. Two samples exhibit neither a steep rise in attenuation nor a velocity anomaly. A number of explanations for the large attenuation are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00116198
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  • 7
    Electronic Resource
    Electronic Resource
    Electron tunneling into superconductive lead-indium alloys subjected to hydrostatic pressure (1977)
    Springer
    Journal of low temperature physics 27 (1977), S. 459-486 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results are presented for electron tunneling studies of superconducting lead-indium alloys (Pb0.88In0.12 and Pb0.64In0.36) as a function of pressure. The pressure dependence of the energy gap Δ0, the reduced energy gap 2Δ0/kTc, and the electron-phonon coupling constant λ show that under pressure the alloys move toward weaker coupling. The numerical agreement with estimates from the strong coupling theory is excellent. The pressure dependence of the transition temperature was measured, and was found to be in good agreement with various theoretical estimates forT c. Grüneisen constants were obtained for the transverse, longitudinal, and localized peak. The well-known McMillan relation for the average square phonon frequency,Mλ〈ω2〉 = const, was investigated. It was found that this relation does not hold as function of pressure in these alloys. An estimate was obtained for the pressure dependence of the band-structure density of states of pure lead. It is found to be about 6.52 times the value predicted for the free-electron case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655282
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  • 8
    Electronic Resource
    Electronic Resource
    Doping dependence of the critical field Hc2 and the transition temperature in Zn doped YBa2(Cu1−xZnx)3O7−δ (1997)
    Springer
    Journal of low temperature physics 107 (1997), S. 491-496 
    Details
    ISSN: 1573-7357
    Keywords: 74.72 Bk ; 74.25 Fy ; 74.25 Ha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present data on the doping dependence of Tc in Zn doped YBa2(Cu1−xZnx)3O6.94, for x up to 10.6%. We find re-entrant behaviour in the range between 9.0 and 10.6% Zn. Data on the magneto-resistance of a sample with extremely low Tc (9% Zn, zero field resistive onset near 3.5 K) show linear normal resistance in all fields down to 1.8 K in 17.5 T. A resistively defined critical field H*, related to Hc2, shows divergent behaviour. The temperature dependence of H* is well represented by expressions derived for the Bose condensation of pre-formed pairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397232
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  • 9
    Electronic Resource
    Electronic Resource
    Dendritic crystal growth in pure4He (1986)
    Springer
    Journal of low temperature physics 64 (1986), S. 165-186 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Dendritic crystal growth of pure hcp and fcc4He was observed at pressures between 210 and 6500 bar. Dendrite morphology depends on fluid supercooling and crystal phase. At large supercooling, dendrites with side arms are observed, whereas at low supercooling dendrites grow without side arms. The morphology of hcp4He dendrites is strongly influenced by crystalline anisotropy. Comparison with present theories of dendrite growth show good agreement with the power law dependencies of velocity, tip radius, and Péclet number on supercooling. Numerically, theory predicts much larger velocities than are observed. The stability parameter σ is found to be much smaller than theoretically predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00685127
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  • 10
    Electronic Resource
    Electronic Resource
    The thermal conductivity of fluid4He and the ratio of thermal conductivities of solid and fluid4He at the melting point (1992)
    Springer
    Journal of low temperature physics 89 (1992), S. 685-688 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694117
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