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  • 1
    Electronic Resource
    Electronic Resource
    Synchrotron x-ray diffraction studies of the lattice and magnetic structure of epitaxial Dy films in LaF3/Dy/LaF3 sandwiches (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4465-4468 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Lattice and magnetic x-ray diffraction from a 2000 A(ring) thick film of Dy, sandwiched by LaF3 films on a GaAs(111) substrate, are reported. The structure was grown by molecular beam epitaxy with the c axis of the Dy parallel to the LaF3 c axis and GaAs [111] axis. We find that the c-axis lattice constant of the Dy has a similar temperature dependence to bulk Dy from room temperature to about 110 K, but below this, the film is different from bulk. The transition to ferromagnetic ordering at ∼86 K exhibits temperature hysteresis which is also evident in the magnetic x-ray scattering and SQUID magnetometry data. This hysteresis may arise from a combination of the strain-energy barrier accompanying the transition and magnetic inhomogeneities in the film. The temperature dependence of the magnetic wave vector is qualitatively similar to bulk, although a weaker dependence is observed below ∼110 K, which is possibly caused by magnetoelastic effects. The magnetic coherence length (310 A(ring)) is significantly shorter than the structural coherence length (730 A(ring)).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349077
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Synchrotron x-ray diffraction studies of the lattice and magnetic structure of epitaxial Dy films in LaF3/Dy/LaF3 sandwiches (abstract) : 35th annual conference on magnetism and magnetic materials San Diego, California (USA) 29 Oct−1 Nov 1990 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5319-5319 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Lattice and magnetic x-ray diffraction from a 2000 A(ring) thick film of Dy, sandwiched by LaF3 films on a GaAs(111) substrate, are reported. The structure was grown by molecular beam epitaxy with the c axis of the Dy parallel to the LaF3 c axis and GaAs [111] axis. We find that the c-axis lattice constant of the Dy has a similar temperature dependence to bulk Dy from room temperature to about 110 K, but below this, the film is different from bulk. The transition to ferromagnetic ordering at ∼86 K exhibits temperature hysteresis which is also evident in the magnetic x-ray scattering and SQUID magnetometry data. This hysteresis may arise from a combination of the strain-energy barrier accompanying the transition and magnetic inhomogeneities in the film. The temperature dependence of the magnetic wave vector is qualitatively similar to bulk, although a weaker dependence is observed below ∼110 K, which is possibly caused by magnetoelastic effects. The magnetic coherence length (310 A(ring)) is significantly shorter than the structural coherence length (730 A(ring)).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348062
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Neutron scattering investigation of a quasi-two-dimensional planar ferromagnet (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3554-3556 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic ordering of stage-2 CoCl2-graphite intercalation compound has been investigated by neutron diffraction. This compound is a layered structure, with ferromagnetic coupling between xy-type spins within the same layer and a much weaker antiferromagnetic coupling between successive layers. The interplanar coupling is sufficiently weak that the ordering occurs in two steps, leaving a temperature window between Tl≈8.8 K and Tu≈9.4 K where the ordering is purely two dimensional. Below Tl the spins become weakly correlated along the c axis, but this correlation never grows beyond two magnetic layers. We have measured the static spin correlation function by neutron scattering. At all relevant temperatures the scattering is markedly two dimensional and consists of two parts: a short-range order term with maximum correlation length and intensity at Tu, and a sharp Bragg-like ridge of constant width, which vanishes above Tu and relates to either long-range order or a power-law decay of the order parameter. Results will be analyzed in light of current theories, in particular, of the vortex binding mechanism proposed by Kosterlitz and Thouless.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340741
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Two dimensional XY type magnetism in intercalated graphite: an elastic and inelastic neutron scattering study (1994)
    Springer
    The European physical journal 93 (1994), S. 277-297 
    Details
    ISSN: 1434-6036
    Keywords: 75.30.K ; 68.65 ; 25.40.F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Stage-2 CoCl2-GIC approximates a two-dimensional easy-plane (XY) ferromagnet on a triangular lattice. It has been found in prior work to order in two steps, with the intermediate phase showing long-ranged ferromagnetic correlations within the intercalate plane, but no correlations between neighboring planes. We have probed the wave vector and temperature dependence of the static and dynamic spin correlations in detail, including measurements of the critical scattering, the quasielastic scattering from vortex diffusion and the spin wave excitations with and without an external magnetic field. Some of the predictions for a Kosterlitz-Thouless type transition are met in this compound, at least qualitatively, including an apparent jump in the spin stiffness at the critical point and the existence of a diffusive central peak in the scattering function possibly originating from vortex autocorrelations. However, there are some inconsistencies between our observations and recent analytical studies as well as Monte Carlo-molecular dynamics simulations of the vortex dynamics that prevent unambigous assignment of the upper critical temperature as a vortex-binding transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01312698
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    Paper (German National Licenses)
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