Predicted properties ofNd1.5Ce0.5Sr2

Abstract

The charge-reservoir oxygen model of superconductivity predicts a critical temperature of T c Ϸ30 K for R 1.5 Ce 0.5 Sr 2 Cu 2 M O 10 (R222M -10) ͑with RϭEu, Sm, and Nd, and M ϭTa and Nb͒, in agreement with the measured values Ϸ28 K. The model also successfully predicts RBa 2 Cu 2 M O 8 (R122M -8) to be an insulator. Other predictions for R222M -10 in need of testing are ͑i͒ it is a p-type superconductor; ͑ii͒ the superconductivity originates primarily in the Sr-O layers, not in the cuprate-planes; ͑iii͒ on cuprate-plane Cu sites, of order ϳ1% Ni should depress T c to zero, while about six times as much Zn will be required to destroy superconductivity; ͑iv͒ magnetic impurities on Cu sites and Sr sites, but not rare-earth sites, will break Cooper pairs; ͑v͒ Pr on Sr sites will suppress T c ; ͑vi͒ the failure of Pr 1.5 Ce 0.5 Sr 2 Cu 2 M O 10 to superconduct is due to the antistructure defect (Pr Sr ϩ3 ,Sr Pr ϩ2 ); ͑vii͒ T c is small because the primary superconducting condensate in the charge-reservoir Sr-O layers is only Ϸ2 Å from the cuprate-planes; and ͑viii͒ the superconductivity should disappear with heavy Ce doping (z→1) in R 2Ϫz Ce z Sr 2 Cu 2 M O 10 . The relationships of R222M -10 to R122M -8, RBa 2 Cu 3 O 7 , and R 2Ϫz Ce z CuO 4 are discussed. ͓S0163-1829͑98͒10517-9͔

Magnetism and superconductivity in Sr YRu Cu O and magnetism in Ba GdRu Cu O

“…These facts indicate that the superconducting hole condensate is in the SrO layer and support the thesis previously advanced by two of us [24][25][26] that, in other materials (such as PrBa 2 Cu 3 O 7 , NdBa 2 Cu 3 O 7 and Nd 2−z Ce z Sr 2 Cu 2 NbO 10 ), the primary superconducting condensate is not in the cuprate planes.…”

Nature of high-temperature superconductivity

“…But we subsequently showed that Pr 2−z Ce z Sr 2 Cu 2 NbO 10 does superconduct. 74 But even today, Gd 2−z Ce z CuO 4 still does not superconduct, while Gd 2−z Ce z Sr 2 Cu 2 NbO 10 does, so there is one remaining major problem: either we must cause Gd 2−z Ce z CuO 4 to superconduct experimentally, or we must admit that the superconducting elements in Gd 2−z Ce z CuO 4 and Gd 2−z Ce z Sr 2 Cu 2 NbO 10 are somewhat different and not ordinary cuprate planes in both materials. Specifically, in Gd 2−z Ce z CuO 4 , the p-type superconducting element is an interstitial oxygen ͑paired with Ce͒, while in Gd 2−z Ce z Sr 2 Cu 2 NbO 10 , the superconducting element is oxygen in the SrO layer.…”

“…Four materials have been successfully predicted to superconduct 22,[72][73][74] and all four of them have been demonstrated to exhibit at least granular superconductivity: PrBa 2 Cu 3 O 7 ͑which superconducts at Ϸ90 K͒, 21 Gd 1.6 Ce 0.4 Sr 2 Cu 2 TiO 10 ͑which superconducted at 12 K͒, 75 Pr 1.5 Ce 0.5 Sr 2 Cu 2 NbO 10 ͑which superconducted at 28 K͒, 76 and Eu 1.5 Ce 0.5 Sr 2 Cu 2 TiO 10 ͑which superconducted at 22 K͒. 77 Of these, all were first granular superconductors; and PrBa 2 Cu 3 O 7 has now been investigated enough that it is clearly a bulk superconductor [26][27][28][29][30][31] ͑see Fig.…”