Magnetic Structure Analysis from Neutron Powder Diffraction Data Using GSAS
- 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)
- 10:50-11:45 am: Overview of representational analysis & FullProf implementation (L.C. Chapon)
- 11:45-12:10 pm: Defining magnetic structures in GSAS/Introduction to exercises (B.H. Toby)
- No host lunch
- 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)
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.Software:
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.The three different refinement approaches are outlined as separate examples on three web pages:
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.
- Two Phase Fit using Magnetic Symmetry. A 50 minute flash movie recording of the demo is also available here (~35 Mb)
- Two Phase Fit without Magnetic Symmetry.
- 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:
Links for the software needed for the exercises are:Papers:
Copyrights to the papers referenced in this workshop are held by the Journals and thus are not distributed on this web site.
- D. B. Litvin, Magnetic space-group types. Acta Cryst. (2001) A57, 729-730. Note that talks refer to tables included as supplementary materials. Alternately see the MAGNETIC SPACE GROUP TYPES section of Daniel B. Litvin's downloads web page (http://www.bk.psu.edu/faculty/litvin/Download.html).
- J. Cui, Q. Huang & B. H. Toby, Magnetic structure refinement with neutron powder diffraction data using GSAS: A tutorial. Powder Diffraction (2006) 21 71-79.