Abstract
Single crystals of and have been grown out of excess Sn with 1% or less incorporation of solvent. The crystals are exceptionally micaceous, are easily exfoliated, and can have dimensions as large as . The single crystals manifest a structural phase transition from a high-temperature tetragonal phase to a low-temperature orthorhombic phase near 85 K and do not show any sign of superconductivity down to 1.8 K. This transition can be detected in the electrical resistivity, Hall resistivity, specific heat, and the anisotropic magnetic susceptibility. In the single crystals this transition is suppressed and instead superconductivity occurs with a transition temperature near 30 K. Whereas the superconducting transition is easily detected in resistivity and magnetization measurements, the change in specific heat near is small, but resolvable, giving . The application of a 140 kOe magnetic field suppresses by only when applied along the axis and by when applied perpendicular to the axis. The ratio of the anisotropic upper critical fields, , varies between 2.5 and 3.5 for temperatures down to below .
8 More- Received 11 June 2008
DOI:https://doi.org/10.1103/PhysRevB.78.014507
©2008 American Physical Society
Synopsis
At last, single crystals
Published 17 July 2008
The ability to grow single crystals of a compound in the family of iron-based superconductors will open the door to a wide range of experiments that were not previously possible.
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