Strong rare-earth size dependence of T-c in RSr(2)Cu(2.85)Re(0.15)O(z)

Abstract

We report a strong rare-earth size dependence of T-c in RSr(2)Cu(2.85)Re(0.15)O(z) (R=rare earth, z approximate to 7.2) compounds, unlike in RBa(2)Cu(3)O(y) compounds. A strong correlation is observed between the superconducting transition temperature and the orthorhombicity of the structure, which itself is R-size dependent. Orthorhombicity is highest for HoSr2Cu2.85Re0.15Oz and ErSr2Cu2.85Re0.15Oz compounds, which also have yielded the highest T-c(approximate to 7.2 K). Significantly, TbSr2CU2.85Re0.15Oz stabilizes in a 1-2-3 structure and also superconducts(T-c approximate to 22 K), whereas EuSr2Cu2.85Re0.15Oz does not superconduct, although it forms a single phase.