KxFe2−ySe2 single crystals: floating-zone growth, transport and structural properties

• Published in: Superconductor science & technology 2012-07, Vol.25 (7)
• Main Authors: Liu, Y, Li, Z C, Liu, W P, Friemel, G, Inosov, D S, Dinnebier, R E, Li, Z J, Lin, C T
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from melts; zone melting and refining; Growth from vapor; Inorganic compounds; Materials science; Methods of crystal growth; physics of crystal growth; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/25/7/075001

Single crystals of superconducting KxFe2−ySe2 have been grown with the optical floating-zone technique under application of 8 bar of argon pressure. We found that large and high quality single crystals with dimensions of ∼ 6 mm ×10 mm could be obtained at the termination of the grown ingot through quenching, while the remaining part of the ingot decomposed. As-grown single crystals commonly represent an intergrowth of two sets of c-axes characterized by slightly different lattice constants. Single-crystal K0.80Fe1.81Se2 shows a superconducting transition at Tc = 31.6 K, leading to a near 100% expulsion of the external magnetic field in magnetization measurements. On the other hand, neutron diffraction data indicate that superconductivity in the sample coexists with a iron-vacancy superstructure and static antiferromagnetic order. The anisotropic ratio of the upper critical field Hc2 for both H c and H ab configurations is ∼ 3.46.