Crystal field fit

(version 3.11.0 Win 7 or MacOS)

Dear all,
First of all, I understand the crystal field (CF) fits are currently under development in Mantid and maybe the issues below are related to that, though as I found some examples (e.g. for INS data, I have tried to run the same scripts with my data with no success until now.

I have tried using both the Python script interpreter and the Fit windows in Mantid. Using the fit windows, with a composite function: adding Lorentzian peaks, polynomial backgound + CrystalFieldSpectrum function, the program crashes and has to be closed. Withing the Python script interpreter I’m following exactly the same procedure as suggested in the example above though I couldn’t fit all the data:

  • My INS data contain CF excitations upon a Dy3+ ion in an intermetallic compound (C3h point symmetry). The data file is energy transfer vs. intensity (x,y), the latter in arb units (counts per seconds);
  • I have the Bmn CF parameters as extracted from fitting susceptibility, MxH and specific heat data and use them as input in Mantid;
  • The Bmn’s I use as input don’t reproduce all the INS experimental peaks. Simulating the spectrum for that set of Bmn just gives one of 3 observed peaks for the measured DeltaE range. Therefore, back in the fit procedure, I need to add the positions from the remaining peaks (as one can do for fitting any function in the Fit windows) and fit the data to get new Bmn parameters set.
  1. How can I add new peaks in a CF fit using the Python script interpreter?

  2. For the Fit window: is the fitting with a composite function done by the convoluting a backg function + 3 lorentzians (3 peaks) + CF spectrum function already available in Mantid?

  3. For the Fit window: If I tried to use the CrystalFieldFunction Mantid gives the error: "You have to set first the Ion ". However, no options to insert the ion + the Bmn parameters are allowed.

Sorry if this topic was posted before but I haven’t found it.

Many thanks for your help.

Hi Raimundo,

How large is your data file? If can send it to me I can try to re-create your problems and see if I can find a way to fix this.

All the best,


Hi Keith,

I have tested the same simulations in Mcphase with the help of a colleague. The problems appear to be related with my expt data.

Thanks for asking.

Hi Raimundo,

Many thanks for letting us know!

All the best,