Superconducting and magnetic properties of TlSr 2 Ca 1 − x R x Cu 2 O 7 [ R =Pr,Tb] (original) (raw)
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Superconducting and magnetic properties of TlSr2Ca1-xRxCu2O7
Physical review. B, Condensed matter, 1995
The magnetic and superconducting properties of the T1Sr2Caq R Cuq07 [R = Pr (+=0. 2-1. 0); Tb (z = 0.6 and 1. 0)] system are reported. The observation of superconductivity in T1Sr2Ca0. 4Pro. sCu20q (T, = 74 K) suggests that the Pr ions are in the trivalent state. The value of the effective magnetic Inoment, p,g-3.15 p,~, for the TISrzCa0. 4Pro. 6CuzOq compound, lies between the free-ion values expected for Pr + (3.58ys) and Pr + (2.54ps). The reduced value of p, s. for the Pr + ion is explained in terms of crystal-field e8'ects. For TlSrz TbCuz07, the Tb magnetic moments order antiferromagnetically at 7.0 K, which is the highest magnetic ordering temperature among the known Tb-containing high-T, related compounds. Superconductivity (T, = 74 and 62 K) and antiferromagnetic ordering (T~= 5 and 6.2 K) coexist in T1Sr2Cao 4Ro sCu20. 7 with R = Pr and Tb, respectively.
Superconductivity and Magnetism in R 2CaBa2Cu5O z (R=La, Pr, Nd and Eu)
Journal of Superconductivity and Novel Magnetism, 2009
A series of compounds R 2 CaBa 2 Cu 5 O z (R = La, Pr, Nd and Eu) have been synthesized by conventional solid state reaction and characterized for their structural, superconducting and magnetic properties. All compounds crystallize with the tetragonal LaBa 2 Cu 3 O z type structure, space group P 4/mmm. Among the four compounds studied here, R = La, Nd and Eu are superconductors with superconducting transition temperatures (T R=0 c ) of 72, 40 and 55 K, respectively. On the other hand, neither superconductivity nor magnetic ordering is seen for R = Pr down to 3 K. The effect of the magnetic field on the susceptibility and (magneto) resistance for the superconducting samples has been investigated. The superconductivity of compounds with magnetic rare-earth ions Nd and Eu exhibit a profound influence of the magnetic field, whereas the application of the magnetic field has a limited effect on the La compound. The Pr compound is paramagnetic and does not exhibit magnetic ordering either.
Structure and superconducting properties of (Tl 0.8 Bi 0.2)(Sr 1.6 Ba 0.4) Ca 2 Cu 3 O 9− δ
The "1223" structural type of high temperature superconductor, (Tlo.sBio.2XSrl.6Ba0.4)Ca2Cu309 -8(referred to as T1,Bi-1223), based on oxides of thallium and bismuth has been prepared by reaction of prereacted powders of (Srl.6Ba0.4)Ca2Cu307 with T1203 and Bi203. The as-synthesized material has a superconducting transition temperature (T c) of 113 K, which is relatively unaffected by post-annealing either in an oxygen or an argon atmosphere. Polycrystalline samples of T1,Bi-1223 exhibit a high persistent current density (Jp) of 1.62 × 107 A/cm 2 at 5 K and 1 tesla, and maintain significant Jp values to temperatures over 60 K. The structure of TI,Bi-1223 has been refined using neutron powder diffraction data. The crystal structure is quite similar to those of T1-1223 related compounds, P4/mmm symmetry with a = 3.8211 A and c = 15.4235 A. The atomic sites of thallium and oxygen in the rock-salt TIO plane are slightly vacant and occupancies of the sites were determined by the neutron diffraction study. 0921-4534/95/$09.50 © 1995 Elsevier Science B.V. All fights reserved SSDI 0921-4534(95)00453-X
Journal of Materials Science-materials in Electronics, 1999
The derivatives of Tl-1212 type phase superconductors with nominal starting compositions Tl0.85Cr0.15)Sr2(Ca1-xRx)Cu2O7 where R = Pr or Nd (Ca series) together with Tl0.85Cr0.15)Sr2(Ca1-xRx)Cu2O7 (Sr series) for x = 0 - 0.5 have been prepared and investigated by d.c. electrical resistance and powder X-ray diffraction analyses. Partial substitution of Ca with Pr or Nd has the advantage of stabilizing the tetragonal
Superconductivity at 124 K in (Tl, Pb)Sr2Ca2Cu3O9
Physica C Superconductivity, 1992
We report the preparation of almost phase pure (T10.sPbo.s)Sr2Ca2Cu3Og, which is characterized by high temperature superconductivity with T¢onset= 130 K, Tcmidpoint= 124 K, Tczero= 122.5 K as measured by electrical resistance, and a diamagnetic onset temperature, Tcm~ of 124 K determined by DC magnetic susceptibility. The new procedure involves synthesizing a material with nominal stoichiometry (Tlo.sPbo.5)Srl.6Ca2.4Cu3Og, which is encapsulated in gold foil and sintered at 950°C for 3 h in oxygen, then sealed in an evacuated quartz tube and finally annealed at 700~ 750°C for 5 ~ l0 days. From the results of X-ray diffraction and energy-dispersive X-ray spectrometry (EDS), we have identified the phase responsible for the superconductivity in the annealed sample to be Tlo.sa(3)Pbo.3s(2)Srt.9t2)Ca2.~ o)Cu309. No superlattice and intergrowth along the a* and c* directions were observed but streaks along the c*-axis were found from microcrystallites of the annealed sample.
Superconductivity of up to 80 K for Tb-123 - TbSr2Cu2.7Mo0.3O7
The Tb-123 phase has been synthesized in single-phase form with the composition TbSr2Cu2.7Mo0.3O7+δ by solid-state reaction route and its phase purity is confirmed by neutron powder diffraction experiments. As-synthesized sample does not show superconductivity down to 5 K. An unusually high antiferromagnetic ordering temperature (T N) of around 7 K is seen for Tb. After 120-atm-O 2 post-annealing, bulk superconductivity is achieved in the compound at around 30 K, without any significant effect on T N. To achieve higher oxygen content and higher T c , the as-synthesized sample is subjected to high-pressure oxygenation (HPO) carried out in a closed cell at 5 GPa and 400 o C in the presence of AgO as an excessoxygen source. This sample exhibited superconductivity onset at around 80 K with a Meissner
Oxidation state and superconducting properties of Y1−xPrxSr2Cu2.85Re0.15O7+δ
Journal of Applied Physics, 1996
Superconductivity exists in orthorhombic Y 1Ϫx Pr x Sr 2 Cu 2.85 Re 0.15 O 7ϩ␦ up to a critical concentration ͑x cr ͒ of 0.65. A progressive decrease in T c occurs as x increases from 0 to 0.65. A further increase in x leads to a tetragonal transformation and as a consequence the T c vanishes; however, the orthorhombicity of these Sr-based compounds is much lower than that observed for the Ba analog, Y 1Ϫx Pr x Ba 2 Cu 3 O 7Ϫ␦ and, hence, the T c. On the one hand, crystal chemistry correlations indicate that the Pr ion is in trivalent state while on the other hand, the stabilizing cation, viz., Re, is in hexavalent state which accounts for the excess oxygen ͑Ͼ7.0͒ in the system. The high x cr value of the Sr series compared to the Ba series ͑x cr ϭ0.55͒ is attributed to the much reduced orbital overlap of the trivalent Pr(4 f) state with the Cu(3d x 2 Ϫy 2)-O(2p) conduction band, via hole localization and/or pair breaking, and is not due to the much discussed hole filling by tetravalent Pr.
Superconductivity in the 70K range in Ca-free Pb_Sr_R_Cu_O oxide system
Solid State Communications, 1990
High temperature bulk superconductivity is well established in several families of copper oxide based systems [1-41, such as, (La,M)2CuO 4, LnBa2Cu307_ 8 and (T1,Bi)m(Ba, Sr)2Can_ 1CunOm+2n+2. More recently, a new family of compounds with general formula Pb2Sr2ACu308+ 8 was reported by Cava et al [5] and confirmed by Subramaniam et al [6]