Chemical
Excision of Tetrahedral FeSe<sub>2</sub> Chains
from the Superconductor FeSe: Synthesis, Crystal Structure, and Magnetism
of Fe<sub>3</sub>Se<sub>4</sub>(en)<sub>2</sub>
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Abstract
Fragments of the
superconducting FeSe layer, FeSe<sub>2</sub> tetrahedral
chains, were stabilized in the crystal structure of a new mixed-valent
compound Fe<sub>3</sub>Se<sub>4</sub>(en)<sub>2</sub> (en = ethylenediamine)
synthesized from elemental Fe and Se. The FeSe<sub>2</sub> chains
are separated from each other by means of Fe(en)<sub>2</sub> linkers.
Mössbauer spectroscopy and magnetometry reveal strong magnetic
interactions within the FeSe<sub>2</sub> chains which result in antiferromagnetic
ordering below 170 K. According to DFT calculations, anisotropic transport
and magnetic properties are expected for Fe<sub>3</sub>Se<sub>4</sub>(en)<sub>2</sub>. This compound offers a unique way to manipulate
the properties of the Fe–Se infinite fragments by varying the
topology and charge of the Fe-amino linkers