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  • 1990-1994  (6)
  • 1985-1989
  • 1990  (6)
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  • 1990-1994  (6)
  • 1985-1989
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  • 1
    Electronic Resource
    Electronic Resource
    Neutron scattering investigation of the ordered state of the nuclear spins in Cu at 60 nK (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5433-5435 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the magnetic structure of the nuclear spin system in Cu below 60 nK by means of neutron scattering. The observation of the nuclear (100) superlattice reflection proves the theoretically predicted antiferromagnetic arrangement of the nuclear spins. The critical field at the lowest temperatures was 0.24 mT. Around 0.1 mT the (100) reflection could not be observed. This is taken as an indication for, possibly, a reorientation phase transitition at this field. Therefore, the phase diagram contains at least two phases. For 0.1 mT〈B〈0.24 mT strong time dependencies of the ordering were observed. At low fields (B〈0.1 mT) nucleation times of the order of 10 s have been observed. These results are discussed with respect to the cooling technique: Adiabatic demagnetization requires constant entropy, a rather unusual way to bring a system from the paramagnetic to the ordered phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344580
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Neutron scattering studies of the spin dynamics in nonlinear and Haldane systems (invited) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5593-5598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In 1D magnets contributions to the spin dynamics which are outside the scope of spin-wave theory can be studied theoretically as well as experimentally. Two prominent examples of such effects are discussed here: solitons and the Haldane gap. We discuss inelastic polarized neutron scattering results on the stability of solitons in CsNiF3 and on the existence of the Haldane gap in CsNiCl3. In both cases, the separate determination of the different correlation functions 〈SαSα〉 with α=x,y,z is essential for definite conclusions: Solitons in CsNiF3 appear to be much more stable than expected from classical theories, and the Haldane gap is the only explanation for the observed gaps in CsNiCl3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345895
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic excitations and phase transition of CsFeBr3 in an external magnetic field (1990)
    Springer
    The European physical journal 81 (1990), S. 75-82 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In CSFeBr3 the Fe2+ ion with effective spin one has locally a singlet ground state (m=0). The antiferromagnetic interactions between neighbouring Fe-ions are too weak as compared with the anisotropy constant to introduce long range order in the absence of an external field. By inelastic neutron scattering we studied the magnetic excitations in an external magnetic field up to 5 Tesla applied along thec-axis. A linear Zeeman splitting was observed with a Landé factorg=2.4. The field renormalizes the dispersion curves in such a way that the exchange interaction has decreasing influence with increasing field. Theoretical calculations according to the excitonic model of Lindgård describe the experimental results very well. At 4.1 Tesla a phase transition appears to a commensurate long range order with a 120° arrangement of the spins in the hexagonal plane. Within the limits of experimental observation this phase transition has no influence on the dynamical behaviour. No critical phenomena could be observed. The dynamical structure factor |G j(ℚ)|2 of the lower Zeeman split modes decreases with increasing field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01454216
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  • 4
    Electronic Resource
    Electronic Resource
    67Zn Mössbauer study of Cu−Zn alloys at high pressure (1990)
    Springer
    Hyperfine interactions 54 (1990), S. 759-765 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The high-resolution 93.3-keV Mössbauer resonance in67Zn was used to investigate Cu−Zn alloys (brass) containing 16.6 wt.% Zn (α-phase) and 50.5 wt.% Zn (β'-phase) at pressures up to 6.2 GPa and at 4.2 K. The recoil-free fraction and the center shift change linearly with reduced volume. The decrease of the center shift is due to the second-order Doppler effect which is partially compensated by the increase of the s-electron density at the67Zn nucleus when the conduction electrons are compressed. In α-brass short-range order leads to four different Cu−Zn configurations. One of them exhibits a center shift which nearly coincides with that of the β'-phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396125
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  • 5
    Electronic Resource
    Electronic Resource
    67Zn Mössbauer study of lattice-dynamical effects and hyperfine interactions in ZnF2 (1990)
    Springer
    Hyperfine interactions 55 (1990), S. 1159-1164 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the high-resolution 93.3-keV transition in67Zn we studied the temperature dependence of the Lamb-Mössbauer factor (LMF), the center shift, and the quadrupole interaction in polycrystalline ZnF2 in the temperature range between 4.2 and 55.3 K. The LMF is anisotropic within the whole temperature range. The electric quadrupole tensor characterized byeV zz Q/h=+(8.2±0.1) MHz and η=(0.15±0.02) is independent of temperature. The results on the isomer shift (relative to ZnO) and on the electric quadrupole tensor are in very good agreement with recent theoretical cluster calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397142
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  • 6
    Electronic Resource
    Electronic Resource
    Phenol/cresol-formaldehyde resin characterization and contribution to product hardness (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 257-262 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Lot-to-lot variations in a phenol/cresol-formaldehyde resin were fully characterized. Resin property-product hardness relationships were examined to elucidate the cause of variable hardness in product insulators and to establish acceptance criteria for the resin. A high methylol content (φCH2OH), determined by quantitative carbon-13 nuclear magnetic resonance (13C-NMR), and a narrow molecular weight distribution (MWD), determined by size exclusion chromatography, were found necessary for resin to produce insulator meeting the minimum Shore D durometer specification of 40.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300502
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