Growth, Annealing Effects on Superconducting and Magnetic Properties, and Anisotropy of FeSe1-xTex ($0.5\leq x\leq 1$) Single Crystals

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Single crystals of FeSe1-xTex ($0.5\leq x\leq 1$) have been grown by the Bridgman method. After annealing them at 400 °C for 100 h in vacuum, single crystals of $x=0.5--0.9$ have exhibited bulk superconductivity. Anisotropic properties of the electrical resistivity and upper critical field, $H_{\text{c2}}$, have been investigated for the single-crystal FeSe1-xTex with $x=0.6$. It has been found that the in-plane resistivity, $\rho_{ab}$, shows a metallic temperature-dependence, while the out-of-plane resistivity, $\rho_{c}$, shows a broad maximum around 100 K. The resistivity ratio, $\rho_{c}/\rho_{ab}$, is 44 and 70 at 290 K and just above the superconducting transition temperature, $T_{\text{c}}$, respectively. The anisotropic parameter, $\gamma\equiv H_{\text{c2}}^{\|}/H_{\text{c2}}^{\bot}$ (superscripts $\parallel$ and $\perp$ indicate field directions parallel and perpendicular to the $ab$-plane, respectively.), is estimated as 2.7 just below $T_{\text{c}}$.
2010-08-15