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  • 1
    Digitale Medien
    Digitale Medien
    A modified dual-slope method for heat capacity measurements of condensable gases (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3841-3845 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A high resolution nonadiabatic method for measuring the heat capacity (CP) of bulk samples of condensable gases in the range of 7.5–70 K is described. In this method CP is evaluated by directly comparing the heating and cooling rates of the sample temperature for two algebraically independent heat pulse sequences without explicit use of the thermal conductance between sample and thermal bath. A fully automated calorimeter for rapid measurement of CP of molecular solids utilizing this technique is presented. The technique along with the automated calorimeter with a provision to apply external electric and magnetic fields is particularly useful for the study of continuous phase transitions in molecular solids as well as field induced changes in the heat capacity. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1290040
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  • 2
    Digitale Medien
    Digitale Medien
    Very high sensitivity ac capacitance bridge for the dielectric study of molecular solids at low temperatures (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 4055-4058 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: An ac capacitance bridge with excellent stability and two parts per billion resolution in the real part of the dielectric constant at temperatures ranging from 4.2 to 80 K and in the audio frequency range (0.2–20 kHz) is reported. The method uses commercially available components as well as few homemade cables and capacitors. Construction details and data on the resolution are presented. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1150035
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  • 3
    Digitale Medien
    Digitale Medien
    Ultralow power low noise ultrahigh frequency magnetic resonance spectrometer (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 157-162 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We describe a simple marginal oscillator that operates at ultralow power dissipation (≥20 μW at 750 MHz) for use in ultrasensitive low noise magnetic resonance detection at very low temperatures. We have operated the circuit down to 0.6 K with the sample maintained below 20 mK and in magnetic fields up to 4.0 T. The samples are maintained at mK temperatures by physically separating the sample from the rf coil.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1142980
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  • 4
    Digitale Medien
    Digitale Medien
    Ultra-Low Temperature Thermometry Using Zeeman Perturbed NQR (1998)
    Springer
    Journal of low temperature physics 110 (1998), S. 763-778 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report the results of measurements of the magnetic field perturbed nuclear quadrupole resonance (NQR) lines of powdered Sb immersed in liquid 3He at low temperatures. The magnetic field was used to separate the frequencies of the allowed transitions between the $$I_Z = \pm \frac{1}{2}$$ and $$\frac{3}{2}$$ levels that correspond to the zero field NQR absorption at 11.5289 MHz for121 Sb. The spectrum for the powder sample consists of two sharp lines with known separation. The ratios of the intensities of these two lines depends only on the difference in thermal population of the nuclear spin levels and can be used for thermometry at very low temperatures. Pulsed NQR measurements of this intensity ratio from 0.25 to 1.45 mK were in good agreement with the expected Boltzmann distributions. Temperature resolutions of 20% could be achieved for signal integration times of ∼ 1 hour.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022610726294
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  • 5
    Digitale Medien
    Digitale Medien
    Nuclear Spin Relaxation of Powdered Metallic Antimony in Liquid 3He (1998)
    Springer
    Journal of low temperature physics 112 (1998), S. 21-45 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Nuclear spin relaxation studies have been carried out to determine the surface relaxation of powdered Sb immersed in liquid 3 He. The surface relaxation mechanism was observed to be significantly more effective than the bulk Korringa relaxation rate for temperatures T 〈 75 mK. This surface relaxation is attributed to the modulation of the dipole-dipole interaction between the Sb spins at the metal surface and the 3 He spins in the solid-like layer on the surface by the quantum zero-point motion of these 3 He atoms. The total relaxation has been analyzed in terms of the surface relaxation and the spin diffusion through the bulk of the Sb particles. The experimental results are in excellent agreement with the theory developed for this system. Replacement of the 3 He by 4 He removes the surface relaxation component and restores the relaxation rates to the bulk value.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022289811309
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  • 6
    Digitale Medien
    Digitale Medien
    Coupling of the Nuclear Spin Alignment of Quadrupolar Nuclei to 3He at Interfaces (1998)
    Springer
    Journal of low temperature physics 113 (1998), S. 323-328 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Measurements of the relaxation of nuclear spin alignments have been carried out using NQR spin echo studies of powdered antimony in contact with liquid 3 He. This system differs from previous studies of the relaxation and magnetization coupling of 3 He at surfaces because the magnetizations 〈 S z 〉≃ 0. The spin alignments 〈 S z 2 〉 are the relevant dynamical variables. The analysis of the experimental results shows that the coupling of the nuclear spin alignment of the antimony nuclei to the magnetization of the 3 He nuclei is determined by the spectral density of the fluctuations of the spin-spin dipolar couplings at the interface. This power density is attributed to the zero-point motions (atom-atom and atom-vacancy exchange) of the 3 He atoms on the surface of the metal particles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022558919066
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  • 7
    Digitale Medien
    Digitale Medien
    Nuclear relaxation in bcc3He for large molar volumes (1982)
    Springer
    Journal of low temperature physics 48 (1982), S. 495-501 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report the results of measurements of longitudinal and transverse nuclear relaxation timesT 1 andT 2 in bcc3He at 300 mK and at a Larmor frequency of 3 MHz for molar volumes 22.6≤V≤24.9 cm3. It is found, even in this extended range of molar volumes, that the relaxation times increase withV as $${\text{T}}_{1,2} \propto {\text{V}}^{\gamma _{1,2} } $$ , with γ1=19±1 and γ2=18±1.5. This molar volume dependence has also been found in various thermodynamic data, including recent results of pressure measurements through the nuclear ordering temperature. This “universality” in molar volume dependence remains unexplained within the context of the present models of multiple exchange.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00681857
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  • 8
    Digitale Medien
    Digitale Medien
    New scientific opportunities at very high magnetic fields (1992)
    Springer
    Journal of low temperature physics 89 (1992), S. 159-167 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The establishment of the National High Magnetic Field Laboratory (NHMFL) in Tallahassee, FL and at the Los Alamos National Laboratory NM will provide the U.S. with a unique opportunity to explore new scientific phenomena in magnetic fields that are significantly higher than presently available. The facilities to be developed within the new NHMFL will include continuous fields to 45 tesla and pulsed fields to 200 tesla. We will review some of the promising new areas of the physics of quantum fluids and solids, superconductivity, materials science and engineering, and advanced technologies that will be able to be studied and developed at the new facility. An overview of the scope of the laboratories facilities, planned scheduling and the proposed timetable for the installation of magnet systems for this new national user facility is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00692588
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  • 9
    Digitale Medien
    Digitale Medien
    Low temperature magnetic measurements of NENP (1992)
    Springer
    Journal of low temperature physics 89 (1992), S. 547-550 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The temperature dependent magnetic susceptibility, χ(T), of two samples of the S=1 linear-chain Heisenberg antiferromagnet Ni(C2H8N2)2NO2(ClO4), known as NENP, has been measured from 400 K to 264 µK. Our measurements are in agreement with existing results of other researchers who worked above 1.2 K. Below 1.2 K, χ(T) increases with decreasing temperature. The results suggest that this increase is intrinsic to the NENP and is not a consequence of a single source of paramagnetic impurities in the samples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00694084
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  • 10
    Digitale Medien
    Digitale Medien
    Boron nitride as a substrate for H2 monolayer studies (1992)
    Springer
    Journal of low temperature physics 89 (1992), S. 653-656 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report measurements of the adsorption isotherms of helium and methane on boron nitride. The suitability of using BN as a substrate for studying the two-dimensional, orientational ordering of quantum quadrupoles on a triangular lattice is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00694109
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