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  • 1
    Electronic Resource
    Electronic Resource
    Thulium barium copper oxide: A 90-K superconductor with a potential 1-MG upper critical field (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 371-373 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Upper critical magnetic fields Hc2(T) have been measured resistively for the high-temperature (Tc(approximately-greater-than)90 K) superconductors TmBa2Cu3O9−δ and YBa2Cu3O9−δ in applied magnetic fields H up to 9 T. If H at the resistive midpoint is defined as Hc2, then the upper critical field slopes (dHc2/dT)Tc at the superconducting transition temperatures Tc are respectively −2.8 and −1.1 T/K. The Tm-specimen initial slope is apparently the highest yet reported for 90 K superconductors. Extrapolations from this slope, based on standard, three-dimensional, dirty-limit Werthamer, Helfand, Hohenberg, and Maki theory, yield (1) zero-temperature upper critical fields Hc2(T=0)=99–175 T, where the range is determined by the degree of paramagnetic limitation; (2) Hc2(T=77 K)≈36 T, the upper critical field at the boiling point of liquid nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98445
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  • 2
    Electronic Resource
    Electronic Resource
    EPR, magnetization, and resistivity studies in doped (4-f or 3-d ions) and undoped RBa2Cu3Oy high TC superconductors (R=Y,Pr,Nd,Eu,Gd,Ho,Er, or Yb) (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4202-4202 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured electron paramagnetic resonance (EPR), resistivity, and dc susceptibility from 2 to 300 K for the oxide high Tc superconductors (R)Ba2Cu3Oy (R=Y,Pr,Nd,Eu,Gd,Ho,Er,Tm, or Yb). Selected systems were doped with 3-d ions (Cr,Mn,Fe,Ni,Co, or Zn) or 4-f ions (Gd or Er) which presumably substitute for the Cu or R site, respectively. In the systems studied we have observed an EPR line at low temperatures (T〈40 K), which exhibits an increase in intensity and decrease in field for resonance as the temperature is lowered. The ESR linewidth is also temperature dependent and exhibits a minimum at about 15 K. An additional EPR line that can be associated with a Gd3+, Mn2+ or Er3+ ion was observed for those samples where these ions were present as dilute impurities. In some of the samples another EPR signal is observed with properties that depend on sample preparation conditions. The behavior and origin of all lines will be discussed. The variation of Tc with concentration of the added impurities over the range (1%–15%) will also be presented, and compared with previous studies in other superconducting systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340224
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  • 3
    Electronic Resource
    Electronic Resource
    UFe4P12 and CeFe4P12: Nonmetallic isotypes of superconducting LaFe4P12 (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3073-3075 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The new compound UFe4P12, which was found to be isostructural to superconducting LaFe4P12 and have a lattice constant of 7.7729 A(ring), is a semiconductor and shows ferromagnetic order below 3.15 K. CeFe4P12 is also a semiconductor, and its magnetic susceptibility is unusually small in comparison to LaFe4P12. The semiconducting behaviors of both UFe4P12 and CeFe4P12 seem anomalous and may arise from strong f-electron hybridization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335217
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  • 4
    Electronic Resource
    Electronic Resource
    Superconductivity and normal-state electronic properties of URu3 and UCo: New behavior for U-compound superconductors (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3090-3092 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The compound URu3 has been found to exhibit superconductivity below 0.15 K. Polycrystalline specimens of URu3 and two other U-compound superconductors, UPt3 and UCo, have been investigated by means of ac magnetic susceptibility measurements in zero and finite magnetic fields. Electrical resistivity, dc magnetic susceptibility, and specific-heat measurements on URu3 and UCo reveal non-heavy-fermion behavior for both compounds and evidence for relatively large exchange enhancement of the Pauli paramagnetic susceptibility for UCo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335169
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic susceptibility of CeT3B2 and UT3B2 compounds (T=Co, Ru, and Ir) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3140-3142 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic susceptibility χ of CeT3B2 and UT3B2 compounds (T=Co, Ru, and Ir) has been measured as a function of temperature T for 2 K≤T≤300 K. For each sample, χ is weakly temperature dependent above ∼100 K, and approaches a finite value as T→0, indicative of a nonmagnetic ground state. The intrinsic susceptibility χ0, after correcting for the effect of the impurities at low temperature, ranges from 5.05×10−4 cm3/mole for CeRu3B2 to 1.33×10−3 cm3/mole for UIr3B2. The ratio S=π2k2Bχ0/3μ2Bγ (γ is the electronic specific heat coefficient), a rough gauge of exchange enhancement, ranges from 0.9 for CeIr3B2 to 4 for CeCo3B2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335183
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  • 6
    Electronic Resource
    Electronic Resource
    Low temperature properties of CeOs2 in the C14 and C15 crystallographic Laves phases (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3137-3139 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The compound CeOs2 has been prepared in both cubic C15 and hexagonal C14 Laves phases. Measurements of ac and dc magnetic susceptibility, electrical resistivity, and specific heat have been performed on samples of both phases. The C14 phase has been found to exhibit superconductivity with a superconducting transition temperature Tc of 1.1 K, while the C15 phase does not display superconductivity above 70 mK. The curves of resistivity vs temperature for both phases exhibit strong negative curvature which are reminiscent of valence fluctuation compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335182
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  • 7
    Electronic Resource
    Electronic Resource
    Onset of superconductivity at 107K in YBa2Cu3O7 − δ at high pressure (1988)
    Springer
    Applied physics 45 (1988), S. 365-368 
    Details
    ISSN: 1432-0630
    Keywords: 74.70 Vy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Electrical resistivityρ measurements under pressure have been carried out on the high-temperature superconductor YBa2Cu3O7 − δ as a function of temperature T between 1 and 300 K at various pressures between 8 kbar and 149 kbar. The superconducting transition temperature Tc increases almost linearly with pressure at the rate dTc/dP ∼- 0.13 K/kbar. The onset of Tc, defined as the temperature at whichρ(T) drops to 90% of its extrapolated normal state value, increases from ∼95 K at 8 kbar to 107 K at 149 kbar. These results suggest that higher pressures will yield yet higher values of Tc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617944
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  • 8
    Electronic Resource
    Electronic Resource
    Compounds in mixed phase CeBa2Cu3Oy and TbBa2Cu3Oy systems (1988)
    Springer
    Applied physics 46 (1988), S. 229-232 
    Details
    ISSN: 1432-0630
    Keywords: 74.70Vy ; 75.50Ee
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An analysis of the composition of Ce and Tb barium copper oxide samples with the nominal composition CeBa2Cu3Oy and TbBa2Cu3Oy, prepared with the same solid state reaction method used for the other superconducting rare earth (R) barium copper oxide RBa2Cu3O7-δ compounds, is described. The analysis indicates that these samples are multiphase and consist mostly of 1) the perovskite phases BaCeO3 or BaTbO3, 2) CuO, and 3) BaCuO2. No trace of the oxygen deficient orthorhombic perovskite type structure of YBa2Cu3O7-δ could be found in the X-ray diffraction patterns. Consequently, the compounds do not display superconductivity. The magnetization measurements indicate that BaCeO3 is weakly paramagnetic which is consistent with tetravalent Ce. The BaTbO3 compound exhibits an antiferromagnetic transition at a Néel temperature TN-35 K, and its magnetic susceptibility above TN can be described by a Curie-Weiss law with an effective moment that corresponds to tetravalent Tb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00939268
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  • 9
    Electronic Resource
    Electronic Resource
    Low-temperature properties of pseudoternary R(Rh1−x Ir x )4B4 (R=Ho and Dy) systems (1988)
    Springer
    Journal of low temperature physics 70 (1988), S. 191-216 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Pseudoternary Ho(Rh1−x Irx)4B4 and Dy(Rh1−x Irx)4B4 systems were investigated with respect to the interplay between superconductivity (SC) and long-range magnetic ordering by means of specific heat (C) and upper critical magnetic field (H c2) measurements. For Ho(Rh1−x Irx)4B4 withx≲0.2 and Dy(Rh1−x Irx)4B4 withx≲0.15, ferromagnetic (FM) ordering, reminiscent of spin-1/2 mean-field theory, was observed. In particular, FM ordering in Ho(Rh1−x Irx)4B4 with 0.07≲x≲0.2 was found to destroy SC at a second critical temperatureT c2 below the superconducting transition temperatureT c, and was accompanied by a spike-shaped feature inC atT c2. Coexistence of antiferromagnetic (AFM) ordering with SC was observed in both systems for 0.2≲x≲0.7. The compounds withx≲0.5 exhibited Néel temperaturesT N that were smaller thanT c and enhanced values ofH c2 belowT N. TheT c andT N undergo an abrupt decrease and increase, respectively, nearx≈0.5, and then cross atx≈0.6, above whichT N〉T c. For Ho(Rh1−x Irx)4B4 with 0.275≤x≤0.4, two different AFM transitions were detected in a double-peak feature inC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683252
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  • 10
    Electronic Resource
    Electronic Resource
    Intermediate valence behavior of ternary cerium and uranium transition metal borides (1984)
    Springer
    Journal of low temperature physics 56 (1984), S. 601-616 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Low-temperature specific heat, electrical resistivity, ac magnetic susceptibility, and dc magnetization measurements were made on ternary cerium and uranium transition metal borides with the general formula CeT3B2 (T=Co, Ru, Rh, and Ir) and UT3B2 (T=Co, Ru, and Ir). The compound CeRu3B2 was found to exhibit superconductivity below 0.68 K. The values of the electronic specific heat coefficient range from 9.7 mJ/mole-K2 for CeCo3B2 to 64 mJ/mole-K2 for UIr3B2. The electrical resistivity versus temperature curves of all of the compounds exhibit negative curvature and are reminiscent of valence fluctuation behavior. In the case of CeIr3B2, the electrical resistivity attains a maximum value at 180 K, while the dc magnetic susceptibility has a temperature dependence that is typical of intermediate valence Ce compounds, approaching a finite value at zero temperature. The electrical resistivity of the ferromagnetic compound CeRh3B2 reveals a rapid decrease in spin disorder resistivity below 120 K. The dc magnetic susceptibility of this material can be described as the sum of a constant term and a Curie-Weiss contribution with an effective magnetic moment of 1.01 µB per formula unit and a Curie-Weiss temperature of 119 K. Magnetization measurements on CeRh3B2 yield a saturation magnetic moment of 0.37 µB per formula unit and a Curie temperature of 113 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681814
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