Neutron Diffraction Investigation of the Fe1−δS System

The intensity of the purely magnetic (001) reflection has been investigated as a function of temperature for ${\mathrm{Fe}}_{\text{1−δ}}\mathrm{S}$ samples with $\text{δ\hspace{0.17em}=\hspace{0.17em}0.02}$ , 0.066, 0.099 and 0.107. Samples from the antiferromagnetic $\mathrm{\alpha \prime }$ phase, $\text{δ\hspace{0.17em}=\hspace{0.17em}0.02}$ , 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, $\text{δ\hspace{0.17em}=\hspace{0.17em}0}$ , 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 $\mathrm{\alpha \prime }$ -phase samples, and the appearance of the x-ray powder diffraction photographs suggest that a mixed phase region may exist below the $\mathrm{\alpha \prime }$ transition. Quenching from above the $\mathrm{\alpha \prime }$ 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 $\text{δ\hspace{0.17em}=\hspace{0.17em}0.066}$ , 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 $\text{δ\hspace{0.17em}=\hspace{0.17em}0.066}$ at the $\mathrm{\alpha \prime \prime }$ transition or in the $\gamma$ region. Also no evidence of disorder occurring in the spin system below $T_n$ was observed with either $\text{δ\hspace{0.17em}=\hspace{0.17em}0.099}$ or $\text{δ\hspace{0.17em}=\hspace{0.17em}0.107}$ .