Metal Vacancy Ordering in an Antiperovskite Resulting in Two Modifications of Fe2 SeO.
Small, red Fe2 SeO single crystals in two modifications were obtained from a CsCl flux. The metastable α-phase is pseudo-tetragonal (Cmce, a=16.4492(8) Å, b=11.1392(4) Å, c=11.1392(4) Å), whereas the β-phase is trigonal (P31 , a=9.8349(4) Å, c=6.9591(4) Å)) and thermodynamically stable within a narrow temperature range. Both crystal structures were solved from twinned specimens. The enantiomers of the β-phase appear as racemic mixtures. Selenium and oxygen form two individual interpenetrating primitive cubic lattices, giving a bcc packing. A quasi-octahedrally coordinated iron atom is found close to the center of each surface of the selenium sublattice. The difference between the α- and β-phases is the distribution of iron at 2/3 of the surfaces. α- and β-Fe2 SeO are comparable with metal-vacancy-ordered antiperovskites. Each Fe/O lattice can also be described in terms of vertex-sharing OFe4 tetrahedra, with a crystal structure similar to that of an antisilicate. Iron is divalent and has a high-spin d(6) (S=2) configuration. The β-phase exhibits magnetoelectric coupling.
Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany. martin.valldor@cpfs.mpg.de.
Martin
0000-0001-7061-3492
M
Valldor
Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany.
Taylor
T
Wright
ESRF, The European Synchrotron, 71 Avenue des Martyrs, 38000, Grenoble, France.
Andrew
A
Fitch
Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany.
Yurii
Y
Prots
X-ray diffraction; antiperovskites; chirality; crystal growth; magnetic properties