SYMMETRY ANALYSIS IN NEUTRON-DIFFRACTION STUDIES OF MAGNETIC-STRUCTURES .2. CHANGES IN PERIODICITY AT MAGNETIC PHASE-TRANSITIONS

A study is made of the translational properties of magnetic structures. The first stage of magnetic structure decoding, which is aimed at determining the magnetic lattice of the crystal, is described in detail using the information obtained from neutron diffraction patterns. Attention is given to the necessity of introducing the notion of transition channel which consists in specifying the wave vector star and the set of its arms describing a given transition. For each of the 14 Bravais lattices of the initial crystal we consider all the possible transition channels with symmetric stars and determine the corresponding magnetic lattices. The results are presented as a table which contains magnetic reflections corresponding to each channel. The notion of wave vectors of a magnetic structure is made more precise and the rule of their translation from the diffraction language into that of group theory is given. © 1979.