Magnetic and superconducting properties of doped and undoped double Perovskite Sr ₂YRuO ₆

We report here SQUID (magnetization) measurements, along with supporting specific heat, Raman, SEM (scanning electron microscope), EDX (energy dispersive X-ray) and XRD (X-ray diffraction) measurements, on Cu-doped and undoped double perovskite $\mathrm{Sr}-{2}^{2+}\mathrm{Y}^{3+}\mathrm{Ru}^{5+}\ mathrm{O}-{6}^{2-}$ (abbreviated as SrY2116) system grown as single crystal using high-temperature solution growth technique. These measurements show the undoped system to be a nonmetallic (insulating) spin glass (SG) and the ∼ 5-30% Cu-doped (i.e. Cu-concentration/(Cu∈+∈Ru-concentration) ∼ 5-30%) system to be a spin glass superconductor (SGSC) with T _c (critical temperature) ∼ 28-31 K and superconducting volume fraction, f _sc∼ 2.2-9%. To mention, similar measurements done on undoped and Cu-doped BaY2116 and BaPr2116 systems show for them the same (SG, SGSC) behaviors. However they show a decrease in T _c and f _sc when diamagnetic Y ³⁺ ions are replaced by Pr ³⁺ spins, presumably due to enhanced internal pair breaking, and also decreased Cu-O-Cu overlap, owing to Pr ³⁺ presence; these phenomena are known to exist in the Pr123 compound, PrBa ₂Cu ₃O _7-δ (δ∼ 0), due to ∼ 10% of Pr ³⁺ ions having tendency to occupy Ba ²⁺ sites. Measurements done on undoped and Cu-doped SrHo2116 show similar SG and SGSC properties. Further, the undoped and Cu-doped SrY2116 crystals grown by hydrothermal growth technique (i.e., grown using lower temperature and high pressure) show same behaviors. From these investigations it can be said that the undoped Ru-double perovskites (A ₂BB′- O ₆, B′=Ru) are SG systems and that Cu-doped Ru-double perovskites (A ₂BB′-O _δ, δ∼ 6, B′=Ru _1-x Cu _x, 0<xâ‰0.3) are SG superconductors (SGSCs). Results are discussed.