A study of the doping dependence of Tc in Ba1−xKxFe2As2 and Sr1−xKxFe2As2 films grown by molecular beam epitaxy

• Published in: Physica. C, Superconductivity Superconductivity, 2011-11, Vol.471 (21-22), p.1177-1180
• Main Authors: Yamagishi, T., Ueda, S., Takeda, S., Takano, S., Mitsuda, A., Naito, M.
• Format: Article
• Language: English
• Subjects: Ba1−xKxFe2As2; Doping dependence; Epitaxial films; Iron-based superconductor; Molecular beam epitaxy; Sr1−xKxFe2As2
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/j.physc.2011.05.152

► MBE growth of single-crystalline films of superconducting Ba1-xKxFe2As2 and Sr1-xKxFe2As. ► The key to incorporating volatile K in films is low-temperature (300–350°C) growth in reduced As flux. ► A systematic doping dependence of Tc in Ba1-xKxFe2As2 and Sr1-xKxFe2As2 was studied. ► The highest Tcon (Tcend) is 38.3 K (35.5 K) at x ∼ 0.3 for Ba1-xKxFe2As2, and 33.4 K (31.0 K) at x ∼ 0.4 for Sr1-xKxFe2As2. ► The optimum K-doping level inducing the highest Tc is different in the two systems. Single-crystalline films of superconducting Ba1−xKxFe2As2 and Sr1−xKxFe2As2 were grown at temperatures below 350°C under reduced As flux by molecular beam epitaxy. We performed a systematic study of the doping dependence of Tc in Ba1−xKxFe2As2 for x=0.0 to 1.0 and Sr1−xKxFe2As2 for x=0.0 to 0.5. The highest Tcon (Tcend) so far attained is 38.3K (35.5K) at x∼0.3 for Ba1−xKxFe2As2, and 33.4K (31.0K) at x∼0.4 for Sr1−xKxFe2As2. The optimum K-doping level inducing the highest Tc is different in the two systems. The implication of the results is briefly discussed.