EFFECTS OF SULFUR VACANCIES ON THE CRYSTALLOGRAPHIC AND SPIN-ROTATION TRANSITIONS OF IRON SULFIDE

Sulfur-deficient iron sulfide, Fe1.04S, has been studied in comparison with FeS by Mössbauer spectroscopy at various temperatures ranging from 82 to 600 K. It is found that the 4 at. % sulfur vacancy makes the crystallographic ± transition from the (NiAs, MnP) structure to a superstructure take place abruptly within 5 K with the superstructure stable up to 410 K. The spin-rotation transition of Fe1.04S takes place at 455 K, which is higher by 63 K than that of FeS. The Néel temperature is not affected appreciably by the sulfur vacancy concentration. © 1990 The American Physical Society.