[Ifeffit] fitting simultaneously two different K-edges

[Bruce Ravel]

Maria Elena,

This paper by Scott Calvin is a good place to start nderstanding
multiple data set fitting:

  S. Calvin, et al., Phys Rev B, 66:22, (2002) p. 224405

It is, of course, on a rather different system from the ones you
mention below, but the ideas are excellent and well explained.  The
concepts should be transferable to your measurements.

B



On Saturday 01 May 2010 12:53:44 pm María Elena Montero Cabrera wrote:
> Dear friends, Sam Webb, Bruce Ravel or any other,
> 
> I have XAFS measurements, performed at SSRL at room temperature, of three
> compounds. All compounds have multielemental character and I have K-edge
> XAFS of two elements in each compound. It is desirable to make IFEFFIT
> fitting of both edges simultaneously. In all cases random solution of
> competing elements is assumed, but there are ferroelectricity,
> superconductivity or magnetic behaviors that are desirable to be explained.
> In each case, XAFS would confirm or reject the random character of the
> solution. I am not such an expert for resolving by myself how to fit
> together two edges using Artemis software. I'll present each case in the
> following:
> 
> 1. rutheno-cuprate (Ru1-xNbx)Sr2Eu1.4 Ce0.6Cu2O10+δ compounds series was
> studied in both Ru and Nb K-edges. Changes in interatomic distances that
> could be obtained by EXAFS would tell something about oxygen octahedra
> around Ru and Nb.
> 
> 2. g-Fe1-xCrxO3 maghemite for x=0.25, 0.5 and 0.75 was investigated by XAFS
> in both Fe and Cr K-edges. Possible distortion of oxygen octahedra around
> both Fe(III) and Cr(III) cations would tell something about not confirmed
> ferroelectricity.
> 
> 3. LaFeNiTiO3 has been confirmed to display magnetic behavior and was
> studied by its Fe and Ti K-edges. Interatomic distances that could be
> obtained by EXAFS are interesting for checking possible preferential
> occupation of sites by Fe or Ti atoms.
> 
> Would any of you, please, suggest how to use Artemis or Sixpack for solving
> these problems?
> Sincerely yours
> 

-- 

 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

 My homepage:    http://xafs.org/BruceRavel
 EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/