Phase separation and metallic conductivity in Tl0.4K0.4Fe2−ySe2−xSx
1 High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China Hefei 230026, PRC
2 Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China Hefei 230026, PRC
Received: 21 September 2012
Accepted: 2 November 2012
We study the effects of S-doping on the microstructure, magnetic and transport properties of the Tl0.4K0.4Fe2−ySe2−xSx superconductor. At low doping level (x ⩽ 0.8), the samples exhibit behaviors similar to those of the parent sample, i.e., the occurrence of phase separation into a Fe-vacancy phase, a charge ordering phase and an undistorted phase; the presence of a “hump”-like feature in the resistivity curves; and the development of antiferromagnetic order well above room temperature. In sharp contrast, the samples with x ⩾ 1.0 all exhibit metallic-like behavior without displaying superconductivity. And these samples are chemically phase separated into a S-poor Tl0.4K0.4Fe2−ySe2−xSx-phase and a S-rich Tl0.4K0.4Fe2−yS2-phase. Interestingly, the Fe-vacancy phase is absent in these samples, accompanied with the disappearance of semiconducting-like conductivity at high temperature and the depression of superconductivity. The charge ordering phase is responsible for the metallic behavior in heavily doped samples.
PACS: 74.25.F- – Transport properties / 74.62.Dh – Effects of crystal defects, doping and substitution / 74.70.Xa – Pnictides and chalcogenides
© EPLA, 2012