High-pressure neutron-diffraction study of FeS

Data collected at 4. 0 GPa for the MnP-type FeS-II phase show that the transition to this phase is accompanied by a 90^ magnetic moment reorientation. Nuclear and magnetic Rietveld refinements show that the observed FeS-II reflection intensities are consistent with a type-I collinear antiferromagnetic structure with moments aligned along the orthorhombic b axis. Neutron data collected for the monoclinic FeS-III phase at 9 GPa support the loss of room-temperature magnetic order.