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تسجيل مستخدم جديدNew Alkali-Metal- and 2-Phenethylamine-Intercalated Superconductors $A_x$(C$_8$H$_{11}$N)$_y$Fe$_{1-z}$Se ($A$ = Li, Na) with the Largest Interlayer Spacings and $T_mathrm{c}$ $sim$ 40 K
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New FeSe-based intercalation superconductors, $A_x$(C$_8$H$_{11}$N)$_y$Fe$_{1-z}$Se ($A$ = Li, Na), with $T_mathrm{c}$ = 39-44 K have been successfully synthesized via the intercalation of alkali metals and 2-phenethylamine into FeSe. The interlayer spacings, namely, the distances between neighboring Fe layers, $d$, of $A_x$(C$_8$H$_{11}$N)$_y$Fe$_{1-z}$Se ($A$ = Li, Na) are 19.04(6) and 18.0(1) {AA}, respectively. These $d$ values are the largest among those of the FeSe-based intercalation compounds and are understood to be due to the intercalation of two molecules of 2-phenethylamine in series perpendicular to the FeSe layers. It appears that the relationship between $T_mathrm{c}$ and $d$ in the FeSe-based intercalation superconductors is not domic but $T_mathrm{c}$ is saturated at ~ 45 K, which is comparable to the $T_mathrm{c}$ values of single-layer FeSe films, for $d$ $geq$ 9 {AA}.
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New superconductors, Li$_x$(C$_n$H$_{2n+3}$N)$_y$Fe$_{1-z}$Se ($n$ = 6, 8, 18), have been synthesized via the co-intercalation of linear monoamines together with Li into FeSe. The distance between neighboring Fe layers expands up to 55.7 {AA} for n =
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terlayer spacing between neighboring Fe layers, d, has been observed. It has been found that a new phase of Lix(C6H16N2)yFe2-zSe2 with d= 10.30(2) {AA} and Tc = 41 K different from the as-intercalated phase is stabilized owing to the possible stable inclination of HMDA intercalated between FeSe layers. This result supports the domic relation between Tc and d in the FeSe-based intercalation superconductors. The reason why Tc increases with a decrease in d through the post-annealing is discussed.
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