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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5863-5865 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High field (up to 5 T) magnetization measurements were performed on both bulk and field-aligned powder samples of RNi2B2C (R=Dy, Ho) magnetic superconductors. For Tc=3.8 K, a DyNi2B2C superconductor with antiferromagnetic Néel temperature TN of 10–11 K, and anomalous field-induced weak-ferromagnetic transitions were observed above the superconducting upper critical field Hc2(2 K) of 1.75 kG. The aligned powders show distinct hysteresis characteristics for both fields applied parallel and perpendicular to the tetragonal basal plane. For Tc=7.8 K, HoNi2B2C has an incommensurate magnetic ordering temperature Tm of 6 K and TN of 5.2 K. Anomalous field-induced weak-ferromagnetic transitions were also observed below TN. No hysteresis can be detected for TN〈T〈Tm. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The systematic variation of anomalous Pr antiferromagnetic ordering temperature TN(Pr) for the two-CuO2-layer cuprate system MA2PrCu2Oy (M=Cu, Hg, Tl, Pb; A=Ba, Sr) was verified through the observation of a new Hg-1212 HgSr2PrCu2O6+δ tetragonal compound with a TN(Pr) of 6 K and a Pr—O bond length of 2.492 A(ring) between Pr and oxygen in the adjacent CuO2 layers. For the tetragonal/orthorhombic 1212 compounds including the PrBa2Cu3O7−y system, TN(Pr) was found to decrease monotonically with increasing Pr—O distance. The importance of Pr-O-Pr superexchange magnetic coupling is expected for all two-CuO2-layer MmA2PrCu2Oy m212-type (m=1, 2, 3) compounds. A similar Pr anomaly in the 2212-type system was first observed on the new tetragonal (Pb0.5Cu0.5)2(Ba0.5Sr0.5)2PrCu2O8 compound with a high TN(Pr) of 9 K. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6568-6570 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Cu spins in TlBa2PrCu2O7 order at TN≈370 K with a spin structure that is collinear and is characterized by the {1/21/21} wave vector, where the nearest neighbor spins are aligned antiparallel along all three crystallographic directions. If 50% of the Ba atoms are randomly replaced by the smaller Sr atoms to form Tl(BaSr)PrCu2O7, the TN of the Cu spins reduces to 350 K but the magnetic structure that forms below TN is the same. However, at T≈20 K the Cu spins undergo a change in structure, and the spin arrangement is then characterized by the {1/21/21/2} wave vector below T≈12 K. The ground state spin structure of the Cu ions in Tl(BaSr)PrCu2O7 is hence noncollinear, where the spin directions of the nearest neighbor Cu ions in the ab plane remain collinear and antiparallel while along the c axis they are orthogonal. These results demonstrate that the atoms in the BaO layers are also actively participating in the coupling between the Cu ions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5362-5364 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural and magnetic properties of the new Bi-doped Gd2−xBixCuO4 system are reported. With the doping of larger trivalent Bi3+ ions, the T′ phase solubility region is retained in the range of 0≤x≤0.1. Weak ferromagnetic or canted antiferromagnetic ordering temperature TN(Cu) of Cu moments decreases from 282 K for Gd2CuO4 to 258 K for Gd1.93Bi0.07CuO4 and 256 K for Gd1.9Bi0.1CuO4. Due to small internal field Hint associated with weak ferromagnetic order, the spin reorientation temperature Tsr(Cu) is field dependent and decreases from 24 K in 1 G to 12 K in 1 kG for Gd1.95Bi0.05CuO4. Preliminary powder x-ray Rietveld refinement analysis using the T′ phase ideal oxygen position indicates a large temperature factor B for the oxygen sites in the Cu–O plane and suggests that the degree of oxygen structural distortion may be closely related to the strength of weak ferromagnetic order. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6789-6791 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two new quaternary borocarbide phases were discovered in the Y–Ru–B–C system: the (1111) YRuBC phase of the LuNiBC-type structure with tetragonal lattice parameters a=3.625–3.630 Å and c=7.775–7.874 Å, and the (1221) YRu2B2C phase of the LuNi2B2C-type structure with tetragonal lattice parameters a=3.742–3.787 Å and c=10.278–10.453 Å. Bulk superconductivity of 9.7 K was observed from transport and magnetic measurements for the annealed YRu2B2C sample with a short Ru–Ru bond length d(Ru–Ru)=(square root of)2 a/2=2.646 Å. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 1463-1468 
    ISSN: 1573-7357
    Keywords: 74.10,+v ; 74.25.Bt, Ha ; 74.72.−h ; 74.72.Jt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of physical properties were performed on the PrBa2Cu4O8-δ sample prepared by the sol-gel method and sintered in I atm oxygen pressure. Instead of exhibiting superconductivity as for R Y or Gd in the RBa2Cu4O8-δ compound. This compound is unstable, insulating but metallic-like at low temperatures. No superconductivity was observed down to 2 K. Since PrBa2Cu4O8-δ can be re-written as Cu2Ba2PrCu2O8-δ which is a compound of two CuO2-layers and two CuO-chains, the possibility of anomalous Pr antiferromagnetic ordering around 18 K observed from preliminary magnetic data and the effect of oxygen stoichiotmetry parameter δ on the metal-insulator transition are explored.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Magnetic measurement and powder X-ray Rietveld analysis are performed on oxygenated Pr 1.5 Ba 1.5 Cu 3 O 7.2 cuprate. This tetragonal compound with lattice parameters a = 0.38916 nm and c = 1.16177 nm is found to form the TlBa 2 CaCu 2 O 7 1212-type structure when written as Cu[Ba 1.5 Pr 0.5 ]PrCu 2 O 7.2. Low temperature magnetic data indicate that anomalous Pr order temperature T N (Pr) decreases from 18 K for orthorhombic PrBa 2 Cu 3 O 6.9 to 10.5 K for Pr 1.5 Ba 1.5 Cu 3 O 7.2. The increasing Pr-O bond length with decreasing T N indicates that Pr ordering is closely correlated with the wave function overlap between Pr-4f orbital and O-2p π orbital in the CuO 2 bi-layers.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 1641-1646 
    ISSN: 1573-7357
    Keywords: 76.60−k ; 74.70−b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 195Pt-,139La- and11B-NMR have been investigated in quaternary RM2B2C (R=Y, La, Th and M=Ni, Pd, Pt). The electric quadrupole frequency of139La changes more than 5 times in magnitude from M=Ni to Pt, indicating that the hybridization of La-5d and d-electrons of M-element changes largely. The analysis of11B and139La spectra shows also the large change of the magnetic anisotropy with R and M element, i.e., χII c〉χII ab in LaNi2B2C, but χII c〉χII ab YNi2B2C.The data of T1T and K of195Pt and11B are consistent with the band effects and with no evidence of strong antiferromagnetic correlation effects.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 379-396 
    ISSN: 0271-2091
    Keywords: rotating flow ; three-dimensional rectangular channel ; pseudospectral matrix method ; eigenvalue decomposition ; two- and four-cell flow pattern ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A Fourier-Chebyshev pseudospectral method is used for the numerical simulation of incompressible flows in a three-dimensio nal channel of square cross-section with rotation. Realistic, non-periodic boundary conditions that impose no-slip conditions in two directions (spanwis e and vertical directions) are used. The Navier-Stokes equations are integrated in time using a fractional step method. The Poisson equations for pressure and the Helmholtz equation for velocity are solved using a matrix diagonalization (eigenfunction decomposition) method, through which we are able to reduce a three-dimensional matrix problem to a simple algebraic vector equation. This results in signficant savings in computer storage requirement, particularly for large-scale computations. Verification of the numerical algorithm and code is carried out by comparing with a limiting case of an exact steady state solution for a one-dimensional channel flow and also with a two-dimensional rotating channel case. Two-cell and four-cell two-dimensional flow patterns are observed in the numerical experiment. It is found that the four-cell flow pattern is stable to symmetri cal disturbances but unstable to asymmetrical disturbances.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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