Howard A. Blackstead

MUON SPIN ROTATION IN SR2YRU1-UCUUO6

The magnetic and superconducting behaviors of sintered Sr{sub 2}YRu{sub 1{minus}u}Cu{sub u}O{sub 6} (for u = 0.05, 0.10, 0.15) were probed using transverse- and zero-field muon spin rotation ({mu}{sup +}SR). In general, positive muons are attracted to oxygen ions in the high-{Tc} oxides, and so, Sr{sub 2}YRu{sub 1{minus}u}Cu{sub u}O{sub 4} layers and those associated with the SrO-layer oxygen. The transverse- and zero-field data for all three stoichiometries u exhibit a sudden onset of magnetic structure at T{sub N} {approximately} 30 K, with a static local field of {approximately}3 kG. This transition is marked by a dramatic increase in the relaxation rate as the temperature decreases below T{sub N}, corresponding to an increased static disordering of the magnetic moments. Above T{sub N} no static fields are observed. Instead the data exhibit a slow dynamic depolarization, presumably due to the rapid fluctuation of paramagnetic moments. Both transverse- and zero-field data also indicate a smaller second component ({approximately}10%) which the authors associate with the SrO layer, exhibiting superconducting behavior in transverse field with an observed {Tc} {approx} T{sub N} {approximately} 30 K.The magnetic and superconducting behaviors of sintered Sr2YRu1-uCuuO6 (for u=0.05, 0.10, 0.15) were probed using transverse- and zero-field muon spin rotation (μ+ SR). In general, positive muons are attracted to oxygen ions in the high-Tc oxides, and so, Sr2YRu1-uCuuO6 should (and does) present two types of μ+ sites, those associated with the oxygen in the YRuO4 layers and those associated with the SrO-layer oxygen. The tranverse- and zero-field data for all three stoichiometries u exhibit a sudden onset of magnetic structure at TN~30 K, with a static local field of ~3 kG. This transition is marked by a dramatic increase in the relaxation rate as the temperature decreases below TN, corresponding to an increased static disordering of the magnetic moments. Above TN no static fields are observed. Instead the data exhibit a slow dynamic depolarization, presumably due to the rapid fluctuation of paramagnetic moments. Both transverse- and zero-field data also indicate a smaller second component (~10%) which we associate with the SrO layer, exhibiting superconducting behavior in transverse field with an observed Tc≈TN~30 K.

Superconductivity in Pr2−zCezSr2Cu2NbO10and in Gd2−zCezSr2Cu2RuO10

The detection of granular superconductivity in Pr222Nb-10 leads to the conclusion that R{sub 2-z}Ce{sub z}CuO{sub 4} (R21-4) compounds and R{sub 2-z}Ce{sub z}Sr{sub 2}Cu{sub 2}NbO{sub 10} (R222Nb-10) compounds both superconduct for R=Pr. The fact that Gd21-4 does not superconduct, but Gd222Nb-10 does, indicates that the superconducting layers are different in the two classes of compounds. Magnetic resonance studies of Gd222Ru-10 and Gd21-4 indicate either that ordered magnetism and superconductivity co-exist in the cuprate-planes or else that the cuprate-planes are not the primary superconducting layers in Gd222Ru-10. (c) 1999 American Institute of Physics.The detection of granular superconductivity in Pr222Nb-10 leads to the conclusion that R 2−z Ce z CuO 4 (R21-4) compounds and R 2−z Ce z Sr 2 Cu 2 NbO 10 (R222Nb-10) compounds both superconduct for R=Pr . The fact that Gd21-4 does not superconduct, but Gd222Nb-10 does, indicates that the superconducting layers are different in the two classes of compounds. Magnetic resonance studies of Gd222Ru-10 and Gd21-4 indicate either that ordered magnetism and superconductivity co-exist in the cuprate-planes or else that the cuprate-planes are not the primary superconducting layers in Gd222Ru-10.

Superconductivity in Pr{sub 2-z}Ce{sub z}Sr{sub 2}Cu{sub 2}NbO{sub 10} and in Gd{sub 2-z}Ce{sub z}Sr{sub 2}Cu{sub 2}RuO{sub 10}

The detection of granular superconductivity in Pr222Nb-10 leads to the conclusion that R{sub 2-z}Ce{sub z}CuO{sub 4} (R21-4) compounds and R{sub 2-z}Ce{sub z}Sr{sub 2}Cu{sub 2}NbO{sub 10} (R222Nb-10) compounds both superconduct for R=Pr. The fact that Gd21-4 does not superconduct, but Gd222Nb-10 does, indicates that the superconducting layers are different in the two classes of compounds. Magnetic resonance studies of Gd222Ru-10 and Gd21-4 indicate either that ordered magnetism and superconductivity co-exist in the cuprate-planes or else that the cuprate-planes are not the primary superconducting layers in Gd222Ru-10. (c) 1999 American Institute of Physics.The detection of granular superconductivity in Pr222Nb-10 leads to the conclusion that R 2−z Ce z CuO 4 (R21-4) compounds and R 2−z Ce z Sr 2 Cu 2 NbO 10 (R222Nb-10) compounds both superconduct for R=Pr . The fact that Gd21-4 does not superconduct, but Gd222Nb-10 does, indicates that the superconducting layers are different in the two classes of compounds. Magnetic resonance studies of Gd222Ru-10 and Gd21-4 indicate either that ordered magnetism and superconductivity co-exist in the cuprate-planes or else that the cuprate-planes are not the primary superconducting layers in Gd222Ru-10.