Year: 2007
Type: article
Abstract: We present a detailed structural investigation of the organic superconductor $\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{C}\mathrm{N})}_{2}]\mathrm{Br}$ at temperatures $T$ from $9\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Anomalies in the $T$ dependence of the lattice parameters are associated with a glasslike transition previously reported at ${T}_{g}=77\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. From structure refinements at 9, 100, and $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the orthorhombic crystalline symmetry, space group $Pnma$, is established at all temperatures. Further, we extract the $T$ dependence of the occupation factor of the eclipsed conformation of the terminal ethylene groups of the BEDT-TTF molecule. At $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, we find 67(2)%, with an increase to 97(3)% at $9\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. We conclude that the glasslike transition is not primarily caused by configurational freezing-out of the ethylene groups.
Source: Physical Review B
Language: Latvian
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1995692376