R(O,F)BiS2 (R: La, Ce, Pr, Nd) superconducting single crystals with different F concentrations are grown using a CsCl/KCl flux. The obtained 1-2 mm-sized single crystals have a plate-like shape and are cleavable along the ab-plane. The crystal structure is tetragonal of space group P4/nmm (#129). The as-grown single crystals exhibit superconductivity at around 3–5 K. The superconducting transition temperature increases with decreasing the ionic radius of the R element. The superconducting anisotropies of the R(O,F)BiS2 single crystals are estimated to be 30–60 according to the effective mass model, whereas the anisotropies for Ce(O,F)BiS2 single crystals are 13–21. The c-axis transport measurements of a single crystal of Pr(O,F)BiS2 under a magnetic field parallel to the ab-plane reveal a “lock-in” state attributed to the Josephson vortex flow. Furthermore, the Ce(O,F)BiS2 single crystals exhibit a magnetic order at the temperature range of 5–7 K that apparently coexist with superconductivity below approximately 3 K.
University of Yamanashi, 7-32 Miyamae, Kofu,
Yamanashi 400-8511, Japan; National Institute for Materials Science,
1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan; E-mail: mnagao@
yamanashi.ac.jp; Tel.: (+81)55-220-8610; Fax: (+81)55-254-3035;
Postal address: University of Yamanashi, Center for Crystal Science
and Technology Miyamae 7-32, Kofu 400-8511, Japan
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