Superconductivity and Intercalation Statein the Lithium-Hexamethylenediamine-Intercalated Superconductor Li$_x$(C$_6$H$_{16}$N$_2$)$_y$Fe$_{2-z}$Se$_2$: Dependence on the Intercalation Temperature and Lithium Content

摘要

The superconductivity and intercalation statein the lithium-andhexamethylenediamine (HMDA)-intercalated superconductorLi$_x$(C$_6$H$_{16}$N$_2$)$_y$Fe$_{2-z}$Se$_2$ have been investigated frompowder x-ray diffraction, thermogravimetric and magnetic susceptibilitymeasurements, changing the intercalation temperature, $T_i$, and the Licontent, $x$. Both Li and HMDA have been co-intercalated stably up to $x$ = 2roughly in the molar ratio of $x : y = 2 : 1$. In the case of $T_i$ =45$^\circ$C, it has been found that both Li and HMDA are co-intercalatedlocally at the edge of FeSe crystals, indicating that both Li and HMDA are hardto diffuse into the inside of FeSe crystals at 45$^\circ$C. In the case of$T_i$ = 100$^\circ$C, on the other hand, it has been found that both Li andHMDA diffuse into the inside of FeSe crystals, so that $T_c$ tends to increasewith increasing $x$ from ~30 K at $x$ = 1 up to 38 K at $x$ = 2 owing to theincrease of electron carriers doped from Li into the FeSe layers.