title: Growth and characterizations of Ba2Ti2Fe2As4O single crystals.
abstract: Single crystals of a new iron-based superconductor Ba2Ti2Fe2As4O have been grown successfully via a Ba2As3-flux method in a sealed evacuated quartz tube. Bulk superconductivity withTc∼ 21.5 K was demonstrated in resistivity and magnetic susceptibility measurements after the as-grown crystals were annealed at 500 °C in vacuum for a week. X-ray diffraction patterns confirm that the annealed and the as-grown crystals possess the identical crystallographic structure of Ba2Ti2Fe2As4O. Energy-dispersive x-ray spectra indicate that partial Ti/Fe substitution exists in the [Fe2As2] layers and the annealing process redistributes the Ti within the Fe-plane. The ordered Fe-plane stabilized by annealing exhibits superconductivity with magnetic vortex pinned by Ti.
authors.affiliation: Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: Yun-Lei
authors.initials: YL
authors.lastname: Sun
authors.affiliation: Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: Abduweli
authors.initials: A
authors.lastname: Ablimit
authors.affiliation: Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: Jin-Ke
authors.initials: JK
authors.lastname: Bao
authors.affiliation: Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: Hao
authors.initials: H
authors.lastname: Jiang
authors.affiliation: Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China; State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: Guang-Han
authors.initials: GH
authors.lastname: Cao
keywords: Ba2Ti2Fe2As4O; iron-based superconductor; single crystal growth