High-pressure synthesis of the indirectly electron-doped iron pnictide superconductor Sr1−xLaxFe2As2 with maximum Tc=22 K

Abstract

Compounds of Sr1−xLaxFe2As2 were synthesized by solid-state reaction at 1273 K, under pressures of 2 or 3 GPa. The Sr1−xLaxFe2As2 phase was dominant up to x=0.5 and superconductivity was observed at x≥0.2. A maximum critical temperature Tc of 22 K and a maximum shielding volume fraction of ∼70% were obtained at x=0.4. This is the first experimental demonstration of electron-doped superconductivity in 122-type iron pnictides, where electrons were doped through aliovalent substitution at the site of the alkaline-earth metal. The optimal Tc was slightly higher than that for the Co-doped (directly electron-doped) samples (19 K) and much lower than that for the hole-doped case (37 K). The bulk superconductivity range was narrower than that for the Co-substituted case and both ranges were much narrower than that for the hole-doped case. These observations revealed that differences in the electron-doping mode (direct or indirect) did not have a prominent effect on the optimal Tc or superconductivity range, compared with differences in carrier polarity.

Source-reported materials — not catalogue approval

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