Superconductivity in Sr-122 Iron Arsenide System by Yttrium Doping

Superconductivity in SrFe$_{2}$As$_{2}$ by interlayer electron doping is achieved for the first time with the substitution of 30 to 50 atomic percent of the strontium with yttrium (Sr$_{1-x}$Y$_{x}$Fe$_{2}$As$_{2})$. In the optimum doped Y = 0.4 sample, Hall effect measurements indicate the injection of extra electrons into the system with negative Hall coefficient below room temperature down to $T_{c}$, and an electron charge carrier density reaching up to 10$^{21}$ cm$^{-3}$ above 200 K. Temperature dependent magnetization measurements indicate the suppression of the magnetic orderings observed in the parent compound at 60 and 210 K upon yttrium doping; while resistivity versus temperature ($R-T)$ measurements show the anomaly above 200 K still persists in the superconducting samples. A maximum onset $T_{c}$ at 26.4 K based on $R-T$ measurement was observed in Sr$_{0.6}$Y$_{0.4}$Fe$_{2}$As$_{2}$. No superconductivity was observed below 0.3 and above 0.5 Y-doping.