Determination of magnetic structures using neutron diffraction

This work introduces and develops methods for a systematic determination of the magnetic structure for a given compound, consistent with neutron diffraction data. The use of the methods is illustrated through the study of the magnetic structures of three compounds (RbMnCl3, CsCoCl3 and CsMnCl3) by neutron diffraction. A summary of the results of the neutron diffraction investigation of the three compounds which are examples of three different magnetic systems, having in common the basic structure of the perovskite, and a transition metal as the magnetic ion is given. Their magnetic structures at low temperatures were solved from the neutron diffraction patterns, and they were all found to be collinear antiferromagnets. Their magnetic symmetry, transition temperatures and magnetic ion moments are summarized. Two methods for the determination of magnetic structures are introduced: the MSG method based purely on geometric symmetry, and the SOPT method based on thermodynamic and symmetry considerations. The use of the two methods is illustrated in this work by application to hexagonal compounds. In conclusion, this study gives: a) solutions for the magnetic structures of the three compounds RbMnCl3, CsCoCl3 and CsMnCl3, b) a list of instructions for the user, which summarize the two methods MSG and SOPT. (B.G.)