The Advanced Photon Source
a U.S. Department of Energy Office of Science User Facility

Magnetic Structure Analysis from Neutron Powder Diffraction Data Using GSAS

This set of web pages provides reference information from the Magnetic Structure Analysis from Neutron Powder Diffraction Data Using GSAS workshop presented at the 2006 American Conference on Neutron Scattering held in St. Charles, IL, June 18-22, 2006.
Workshop Schedule:
  • 9:00-9:05 am: Introduction (B.H. Toby)
  • 9:05-9:50 am: History, Color symmetry & Shubnikov space groups (B. Chakoumous)

Lecture notes: History and Color symmetry & Shubnikov space groups

  • 9:50-10:20 am: Magnetic extinctions classes & common magnetic structure types (R.B. Von Dreele)

Lecture Notes

    Break
  • 10:50-11:45 am: Overview of representational analysis & FullProf implementation (L.C. Chapon)
        Lecture Notes and Accompanying files
  • 11:45-12:10 pm: Defining magnetic structures in GSAS/Introduction to exercises (B.H. Toby)

Lecture Notes

    No host lunch

  • 2:00-4:30 pm: Self-paced exercises -- bring your own laptop.

Demo of 1st exercise as a 50 min. Flash video (~35 Mb)
Exercises:

Three different approaches for how GSAS may be used to fit both structural and magnetic models to a set of neutron powder diffraction data were used for this tutorial, following the examples in the Powder Diffraction paper by Cui, Huang and Toby. The examples are presented here on web pages that provide step-by-step instructions along with explanations, sample output and computer screen images. In these examples, EXPGUI is used as an interface to GSAS where possible, but where EXPGUI does not implement the required GSAS capability, the GSAS EXPEDT program is used instead.

The sample data for this tutorial consist of two files, YBAFEO.GSA, a GSAS ".raw" file, which contains diffraction intensities and their standard uncertainties and YBAFEO.INS, the GSAS instrument parameter file that provides information about these data as well as starting parameters for the refinement.

Alternately, the two files can be downloaded, combined with several other input files that will reduce the amount of typing that needs to be done in the subsequent examples from a single zip file, YBAFEO.zip.

The three different refinement approaches are outlined as separate examples on three web pages:

  1. Two Phase Fit using Magnetic Symmetry. A 50 minute flash movie recording of the demo is also available here (~35 Mb)
  2. Two Phase Fit without Magnetic Symmetry.
  3. Single Phase Fit in Magnetic Supercell.

In addition, three examples of how to either list or visualize spin directions are outlined on three additional web pages:

  1. Listing Magnetic Spins Directions in GSAS.
  2. Visualizing Magnetic Spin Directions GSAS with VRSTPLOT.
  3. Visualizing Magnetic Spin Directions GSAS with DRAWxtl.
Software:

Links for the software needed for the exercises are:
        GSAS & EXPGUI (https://subversion.xray.aps.anl.gov/trac/EXPGUI).
        DRAWXtl (http://lwfinger.com/drawxtl)
        VRweb for windows (source unknown).

Note that GSAS, EXPGUI and DRAWxtl are available for Windows, Linux and Macintosh. VRweb may available for windows and some Unix platforms; I do not know of a VRML1 viewer (needed by VRSTPLOT) for the Mac.
Papers:

Copyrights to the papers referenced in this workshop are held by the Journals and thus are not distributed on this web site.