Neutron Diffraction Investigation of the Fe1−δS System

Abstract

The intensity of the purely magnetic (001) reflection has been investigated as a function of temperature for Fe1−δS samples with δ = 0.02, 0.066, 0.099 and 0.107. Samples from the antiferromagnetic α′ phase, δ = 0.02, exhibit a spin reorientation at a temperature corresponding closely to that at which the susceptibility anomaly occurs (125°C). Preliminary measurements on a stoichiometric sample, δ = 0, suggest that for this composition, two distinct spin reorientations occur, one at 140°C corresponding to the abrupt change in susceptibility and the second at 160°C. The presence of a small (001) reflection at room temperature in the α′-phase samples, and the appearance of the x-ray powder diffraction photographs suggest that a mixed phase region may exist below the α′ transition. Quenching from above the α′ transition produces samples which show no room temperature peak, and whose x-ray patterns indicate only a single phase. An examination of the (001) reflection of samples for which δ = 0.066, 0.099 and 0.107, suggests that for these compositions the spins lie in the hexagonal planes from room temperature to the Néel temperature, 320°C. No anomalies were observed for δ = 0.066 at the α′′ transition or in the γ region. Also no evidence of disorder occurring in the spin system below Tn was observed with either δ = 0.099 or δ = 0.107.