I have carried some neutron diffraction experiments. It is easy to analyse the pattern for samples with ferromagnetic and commensurate antiferromagnetic structures. But now I am not sure how to determine accurately the k-vector for a incommensurate structure.
In FullProf suite, there is a software "K-search". Who know how to use it?
To use k-search, I propose you the following method :
1)You have to identify the magnetic peaks (usually at low 2theta). It can be done by subtracting pattern recorded above magnetic transition temperature and pattern recorded at low temperature (cf. picture 1 : blue recorded above TC and red recorded at T = 10K ; green = difference between the two first pattern highlighting the magnetic peaks). Save the difference data
2) - Using WinplotR, open the difference data file. click on "Point Selection\Select Points" and select your magnetic peaks (in my case, I have selected five peaks).
- Save the peaks with " Point Selection \ Save as...\Save points for k_search".
- Complete the input parameters (Lattice type, cell parameters, k range, ...) and save this input file.
3)launch k-search and select your "*.sat " file. After calculations, the software will propose you a result (cf. picture 2. For me it's a incommensurate structure with k = but the reasoning is the same for incommensurable one).
hope it will help you,
best wishes,
You can find the k vector anambiguously only if you have a single crystal by doing neutron diffraction. By doing k search on neutron powder diffraction data can lead you to ambiguous and wrong results. Why don't you try to get a single crystal?
Dear Christophe Lefevre,
Thank you very much for your help. I tried to do this job following your suggestions. However, it gives me a result which is of large difference from that reported previously. Maybe I need to try both values.
Dear Tapan Chatterji,
Thanks a lot. I know that measurement on single crystal is the best way to determine the propagation vector. The problem is that no device is available to grow single crystal. Anyway, thanks.
- Badges
- Science topic