Magnetic Structures of MnO, FeO, CoO, and NiO

The antiferromagnetic arrangement of moments in MnO, FeO, CoO, and NiO have been investigated by powder neutron diffraction. The results for the four oxides are consistent with a structure in which the magnetic moments are arrayed in ferromagnetic sheets parallel to (111) planes, and the direction of magnetization in neighboring planes is antiparallel. The observation of diffuse neutron scattering limits the precision with which the magnetization direction can be specified. If the diffuse intensity is included with the Bragg scattering, the direction of magnetization in MnO, and NiO lies within the (111) plane; for CoO, the preferred direction is [$\overline{1}\overline{1}7$], intermediate to the (111) plane and the tetragonal axis. The magnetic axis in FeO is perpendicular to the ferromagnetic sheet.