Abstract
We report neutron diffraction studies of FeS single crystals obtained from Rb (x) Fe(2-y) S(2) single crystals via a hydrothermal method. While no [Formula: see text] iron vacancy order or block antiferromagnetic order typical of Rb (x) Fe(2-y) S(2) is found in our samples, we observe C-type short-range antiferromagnetic order with moments pointed along the c axis hosted by a different phase of FeS with an expanded interlayer spacing. The Néel temperature for this magnetic order is determined to be 170 ± 4 K. Our finding of a variant FeS structure hosting this C-type antiferromagnetic order demonstrates that the known FeS phase synthesized in this method is in the vicinity of a magnetically ordered ground state, providing insights into understanding a variety of phenomena observed in FeS and the related FeSe(1-x) S (x) iron chalcogenide system.