Symmetry analysis in neutron diffraction studies of magnetic structures. III

Using the symmetry analysis technique developed in the two earlier papers of this series a study is made of the magnetic structures in spinels (space group Osub(h)7)). The magnetic structures with the wave vector K=0 and those with Knot=0 are considered in detail. As an example, an analysis is given of the magnetic ordering in MgV2O4 which is characterized by the three-arm star [K10] (in Kovalev's notation) and of that in HgCr2S4 where a helical structure corresponding to the star [K6] has been found. For each of the three stars the authors have determined the composition of the magnetic representation and calculated the basis functions of the irreducible representations. For the magnetic structures determined experimentally they have specified the irreducible representations by which these structures should be described. The examples furnished illustrate the typical situations liable to occur when performing symmetry analysis of magnetic structures of crystals. (Auth.)