K sub(x)Fe sub(2-y)Se sub(2) single crystals: floating-zone growth, transport and structural properties

Single crystals of superconducting K sub(x)Fe sub(2-y)Se sub(2) 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 similar to 6 mm x 10 mm could be obtained at the termination...

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Bibliographic Details
Published in:Superconductor science & technology 2012-07, Vol.25 (7), p.075001-1-6
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:
Expulsion
Ingots
Magnetic fields
Neutron diffraction
Quenching
Single crystals
Superconductivity
Superstructures
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Summary:Single crystals of superconducting K sub(x)Fe sub(2-y)Se sub(2) 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 similar to 6 mm x 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 K sub(0.80)Fe sub(1.81)Se sub(2) shows a superconducting transition at T sub(c) = 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 square root 5 x square root 5 iron-vacancy superstructure and static antiferromagnetic order. The anisotropic ratio of the upper critical field H sub(c2) for both H parallel parallel c and H parallel parallel ab configurations is similar to 3.46.
ISSN:0953-2048
DOI:10.1088/0953-2048/25/7/075001