ITC Volume M

ITC Volume M

An exploratory outline of a future volume on magnetic structures for the International Tables of Crystallography, based on commission discussions that began during summer 2013.  Moved here on 22/04/15 from the old CMS Wiki, which is no longer supported.  External input is welcome.

  1. Magnetic symmetry
    • Magnetic symmetry operations
    • Magnetic point groups
    • Magnetic line groups
    • Magnetic plane groups
    • Magnetic space-groups
    • Magnetic superspace groups
    • Magnetic subperiodic groups
  2. Magnetic scattering (both x-rays and neutrons)
    • Magnetic cross sections
    • Magnetic form factors
    • Magnetic diffraction experiments
      • Polycrystalline (powder) neutron diffraction
        • This is probably the largest and most important group.
        • The results are often over interpreted and conclusions may not be unique.
        • Much of directional info and interaction with external constraints is lost.
        • Can be used with or without incident-beam polarization.
      • Single-crystal diffraction with unpolarised neutrons
        • Requires relatively large crystals (~0.5mm^3)
        • Allows collection of larger data sets leading to less ambiguity.
        • Magnetic domains may cause problems.
        • Experiments using external constraints are possible (e.g. magnetic field, electric field, uniaxial stress)
      • Single crystal diffraction with polarised neutrons: polarisation dependence of the scattered intensity
        • Employ either incident or scattered beam polarizers.
        • Details of magnetisation distribution
        • Separation of magnetic and nuclear scattering
        • Structural response to applied constraints
        • Not for Laue experiments due to lack of good white-beam polarizers.
      • Single-crystal diffraction with polarisation analysis
        • Employ both incident and scattered beam polarizers.
        • The experimental relationship between polarisation directions of the incident and scattered beams has three common varieties.
          • Uniaxial: Pi and Pf are parallel
          • XYZ: Allows diagonal elements of the polarisation matrix to be determined
          • Spherical: Allows determination of all elements of the polarisation matrix
        • Unique confirmation of moment directions relative to crystal axes and external constraints.
        • Fine details of complex structures
      • Diffuse neutron scattering from disordered or nanoscale materials
        • Pair-distribution-function analysis of local magnetic order
        • Small-angle scattering from mesoscopic magnetic order
        • Reflectometry studies of magnetic films and surfaces
      • Q-omega neutron spectroscopy of dynamic magnetic structures
      • Resonant X-ray magnetic scattering
      • Non-resonant X-ray magnetic scattering
  3. Magnetic structure
    • Structure types (with examples)
    • Parameterization
      • Commensurate k-vectors
        • Wave approach
        • Supercell approach
        • Representational approach
      • Incommensurate k-vectors
        • Wave approach
        • Representation approach
    • The practical application of magnetic symmetry
    • Magnetic domains
  4. Magnetic physical property tensors

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