GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Spin fluctuations of La2−xSrxCu1−yZnyO4−δ (x=0.14, y=0.012) (abstract) : 37th annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6333-6333 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetism of high-Tc superconductors is still the subject of intensive investigation. Zn substitution for Cu together with removal of oxygen suppresses the superconductivity quickly. We prepared two crystals to perform a neutron scattering study of the spin fluctuations of La2−xSrxCu1−yZnyO4−δ. One is a Zn-doped and deoxygenated crystal La1.86Sr0.14Cu0.988Zn0.012O4−δ (#1) which does not show superconductivity above 1.5 K. The other is a Zn-doped crystal La1.86Sr0.14Cu0.988Zn0.012O4 (#2) which shows superconductivity below 16 K. The incommensurate spin excitations observed previously in superconducting samples1,2 containing no Zn remain in both samples. However, there is significant difference in the spectral weight χ‘(q,ω) at low temperatures between the non-superconducting and superconducting Zn-doped crystals. In crystal #1 the spectral weight at low temperatures is qualitatively similar to that of Zn-undoped non-superconducting samples.3 In crystal #2 the spectral weight at low temperatures is qualitatively similar to that of Zn-undoped superconducting samples.1,2 These results demonstrate that there is an intimate relationship between the magnetism and the superconductivity. We are in the process of further measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352638
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Novel magnetic phenomena in lamellar copper oxide superconductors (invited) (abstract) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4682-4682 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the lamellar copper oxide superconductors, magnetic phenomena play a fundamental role. Pure La2CuO4 is a nearly ideal realization of the two-dimensional, S= 1/2 Heisenberg model, a system of basic interest in statistical physics. Doping with holes has a dramatic effect on the Cu2+-Cu2+ spin correlations. A hole concentration of 2% is sufficient to destroy the Néel state and to produce a novel spin-glass phase. In this talk we will review the results of a series of neutron-scattering studies of the static and dynamic spin fluctuations in the antiferromagnetic, spin-glass, and superconducting regions of the La2−xSrxCuO4 phase diagram. Emphasis will be placed on recent results in the pure material La2CuO4 (Ref. 1) and in the superconductor La1.85Sr0.15CuO4.2 For a general review see Ref. 3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344824
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Spin dynamics in the diluted antiferromagnet MnxZn1−xF2 (invited) (abstract) (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3692-3692 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The problem of spin dynamics in disordered magnets has been a subject of research for the past two decades. Diluted systems are of special interest since they exhibit percolation effects for concentrations near the percolation threshold (xp). For concentrations x〉xp the system should look uniform at long wavelengths and highly disordered at short wavelengths; the latter regime should exhibit fractal geometrical characteristics; specifically, as a function of decreasing wavelength, one might expect a crossover from magnon to "fracton'' behavior. A recent high-resolution inelastic neutron scattering study on a large (8 cm3) single crystal of (Mn0.5Zn0.5)F2 shows just these effects. At T=5 K Mn0.5Zn0.5F2 exhibits very sharp spin waves at small q and ω which become rapidly broader with increasing q; further, the excitations are essentially localized in character at higher energies. In this case by "localized'' we mean extremely broad both in energy at fixed wave vector and in wave vector at fixed energy; the crossover from "magnons'' to "fractons'' occurs when the wave vector is comparable to the inverse pair connectedness ξ−1 for the diluted system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338663
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Phase diagram and phase transitions of Krypton on graphite in the extended monolayer regime (1987)
    Springer
    The European physical journal 69 (1987), S. 347-377 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report high resolution x-ray diffraction studies of the structures and phase transitions of monolayer krypton, adsorbed on both powder and single crystal graphite substrates. A comprehensive series of powder diffraction profiles is used to construct the two dimensional phase diagram. The melting of the $$\sqrt 3 x\sqrt 3$$ commensurate solid is shown to be strongly first order throughout the region where tricritical behavior was previously thought to occur; fluid solid coexistence extends up to the termination of the commensurate phase at 130 K. A disordered weakly incommensurate phase is shown to be a reentrant fluid, a system which may be described as a disordered network of domain walls and which evolves continuously into a more conventional 2D fluid. This evolution is marked by the disappearance of satellite peaks which are caused by the modulation of the overlayer by the substrate. The freezing of the reentrant fluid into the commensurate phase is shown to be consistent with a chiral Potts transition, its freezing into the incommensurate solid consistent with a dislocation binding transition. Single crystal experiments reveal the orientation of the weakly incommensurate phase. The reentrant fluid is found to have no visible orientational fluctuations, manifesting isotropic diffraction peaks. This is attributed to the strong epitaxy of domain walls. The incommensurate solid is shown to undergo an aligned-rotated transition which is well described by zerotemperature calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01307294
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    The bicritical phase diagram of two-dimensional antiferromagnets with and without random fields (1993)
    Springer
    The European physical journal 93 (1993), S. 5-19 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Neutron scattering measurements have been made of the phase diagrams of the nearly two-demensional antiferromagnets Rb2MnF4 and Rb2Mn0.7Mg0.3F4 in a magnetic field applied along thec-axis. In Rb2MnF4 there is at low temperatures a spin-flop phase at fields above 5.5 T which has long range order. The observation of true long range order rather than the algebraic decay of the order characteristic of the two-dimensional XY model is presumably due to subtle anisotropy effects in the plane as well as weak three-dimensional coupling. The phase boundaries of the uniaxial and transverse phases are shown to be consistent with renormalization group predictions for two-dimensional systems. The two lines become exponentially close to each other at low temperatures. The weak three-dimensional coupling moves the bicritical point fromT=0 to a non-zero temperature. The situation is more complex in Rb2Mn0.7Mg0.3F4 because of Ising random field effects. At low fields we observe typical random field metastable behavior with a sharp metastability boundary and a gange of length scales which are time independent below that boundary. At higher fields there are substantial uniaxial fluctuations. The transverse phase boundary and the metastability line appear to intercept atT=0 showing that the random field fluctuations do have a large effect on the phase diagram. The theory of the phase diagrams has been extended to include the random field fluctuations and good agreement is obtained with the observed transverse phase boundary. Unfortunately, there is as yet no theory of the metastable uniaxial phase with which to compare our results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01308802
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    A high resolution synchrotron x-ray study of the weakly-incommensurate phase of high stage bromine-intercalated graphite (1985)
    Springer
    The European physical journal 62 (1985), S. 79-95 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report the results of a high resolution synchrotron x-ray scattering study of the weakly incommensurate stripe domain phase of high stage bromine-intercalated graphite. The translational order in this system is two-dimensional in nature.) We demonstrate power-law behaviour at five harmonics (G) of the mass density wave, and confirm the scaling of the structure factor withG 2. Our results are consistent with recent theories of the two dimensional uniaxial commensurate-incommensurate transition, which are based on an entropically wandering domain wall picture of the incommensurate phase. We demonstrate that, in this system, the domain walls have a width much less than their separation so that significant molecular displacements from the commensurate sites occur within a unit cell. Close to the transition, we observe hysteresis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01303738
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Temperature scaling of the integrated dynamical susceptibility in YBa2Cu3O6.5(T c =50 K) (1992)
    Springer
    The European physical journal 87 (1992), S. 15-19 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic neutron scattering cross section in a crystal YBa2Cu3O6.5(T c =50 K) has been measured for energies between 4.5 meV and 15 meV and temperatures between 10 K and 275 K. From these data we extract the generalized susceptibility integrated around the (π, π) position $$I(\omega ,T) = \int\limits_{(\pi ,\pi )} {dq\operatorname{Im} \chi (q,\omega )_T .}$$ These data are combined with those at 8.3 and 33.1 meV from a previous study. It is found thatI(ω, T) exhibits the simple temperature scaling form found previously in La2−x Sr x CuO4. Specifically, in YBa2Cu3O6.5,I(ω, T)=I(ω, 0)2/πtan−1 (ω/0.9T). Implications of this behavior for the d.c. and infrared conductivity are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01308252
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Nonasymptotic critical 3D-XY behavior for the nematic-smectic-A 1 liquid crystal transition (1993)
    Springer
    The European physical journal 90 (1993), S. 357-360 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High-resolution X-ray data near the nematic (N)-smectic-A 1 (SmA 1) transition are reported for two polar liquid-crystal systems with large nematic ranges. The correlation volume ξ∥ ξ ⊥ 2 , the smectic order-parameter susceptibility σ, and the heat capacityC p of these systems and two other N-SmA 1 systems are in excellent agreement with exact theoreticalpreasymptotic 3D-XY predictions. The importance of correction terms for ξ∥ ξ ⊥ 2 and σ as well asC p is demonstrated. Universal features of the 3D-XY model are obeyed except for anisotropy in the correlation lengths ξ∥ and ξ⊥.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01433060
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Spin dynamics and spin correlations in the spinS=1 two-dimensional square-lattice Heisenberg antiferromagnet La2NiO4 (1995)
    Springer
    The European physical journal 96 (1995), S. 479-489 
    Details
    ISSN: 1434-6036
    Keywords: 75.10.Jm ; 75.25.tZ ; 75.40.−S ; 75.30.Ds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The static and dynamic spin fluctuations in the spinS=1, two-dimensional (2D) square-lattice antiferromagnet La2NiO4 have been studied over a wide temperature range using neutron scattering techniques. The spin correlations in La2NiO4 exhibit a crossover from two- to three-dimensional (3D) behavior as the Néel temperature is approached from above. Critical slowing down of the low-energy spin fluctuations is also observed just aboveT N . The correlation length, ξ(T), and the static structure factor,S(0), have been measured and are compared with recent theoretical calculations for the quantum 2D Heisenberg antiferromagnet using microscopic parameters determined from previous spin-wave measurements. Good agreement for ξ(T) is found with the exact low-temperature result of Hasenfratz and Niedermeyer provided that 2π p s is renormalized by ≈20% from the spin-wave value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313845
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Random field effects in the three dimensional Ising magnet: Fe x Zn1−x F2 (1984)
    Springer
    The European physical journal 58 (1984), S. 15-30 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have carried out a comprehensive neutron scattering study of random field effects in the diluted three dimensional Ising antiferromagnet Fe x Zn1−x F2 withx=0.35 and 0.5. Emphasis is on the global trands from the small to the large random field regimes. It is found, as in previous experiments, that when the system is cooled in a field it evolves from the high temperature paramagnetic state to a low temperature domain wall state. The low temperature peaks are well-described by Lorentzian squared profiles although for thex=0.5 sample extinction made the measurements difficult. In both samples, the results show that in the field-cooled state the correlation length varies asH −v withv=2.2±0.1. In thex=0.35 sample this power law holds over a length scale varying from 2 to 1500 lattice constants. At low fields pretransitional behavior similar to that observed previously in Fe0.6Zn0.4F2 is found. AtT N (H=0) it is found that the correlation length also scales algebraically withH but withv=0.86±0.04. Pronounced history-dependent effects are observed below the phase boundary determined by the peak in the critical scattering. For example, on cooling in zero-field, raising the field and then warming, long range order survives up to the phase boundary; at this point it appears to convert abruptly into the finite correlation length field cooled state although elucidation of the explicit nature of this transition is complicated by rounding due to a concentration gradient. These results are discussed in the context of recent theories incorporating metastability effects as well as recent experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01469433
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...