[Ifeffit] something is wrong with Ruthenium-Oxygen bond amplitudes

María Elena Montero Cabrera elena.montero at cimav.edu.mx
Fri Nov 5 22:49:43 CDT 2010


Thanks a lot, Wayne!
I'll try to see spectra again with SixPack, which is close to SSRL data
collection. I keep in touch. Best regards
  Maria Elena

2010/11/5 Wayne W Lukens Jr <wwlukens at lbl.gov>

> Hi Maria Elena,
>
> Your RuO2 spectrum does not look right to me. Here is a spectrum that I
> obtained on 11-2
> in transmission. The sample is RuO2 powder brushed onto tape (16 layers of
> tape). Feff 7
> fits the data well (amp is 1.1 for the oxygen shell if I allow it to vary).
>  I think you my have either a sample or data collection issue.  Since you
> have a good XRD, I would suspect the latter.
>
>  For what it's worth, I have had problems with Ru metal and Feff and had to
> reduce amp to around 0.7 (if I remember correctly) to get a good fit.
>
> Sincerely,
>
> Wayne
>
>
>
>
> 2010/11/5 María Elena Montero Cabrera <elena.montero at cimav.edu.mx>
>
> Hi Scott!
>> Thanks a lot for your interest. The physical form was powder, and they
>> were measured by transmission and fluorescence. We have tried firstly the
>> fitting of fluorescence spectra, but we have obtained that low amplitude
>> values. So I have though we have autoabsorption, and decided to do the
>> fitting of transmission spectra. They are not exactly the same, close to the
>> edge fluorescence spectra have lower mu(E). I remember that Sam Webb told me
>> that the K edge jump was good in the absorption spectra, after calculating
>> the thickness with Hephaestus.  In that fitting we have obtained the same
>> "wrong" values. Then we decided to do the fitting of RuO2, and we have
>> obtained again the low amplitudes. Now I don't know what to do.
>> Regards
>>    Maria Elena
>>
>>
>> 2010/11/5 Scott Calvin <dr.scott.calvin at gmail.com>
>>
>> Hi Maria,
>>>
>>> What was the physical form of the samples (powder, thin film, etc.) and
>>> how were they measured (transmission, fluorescence, ...)? Sometimes this
>>> kind of thing can stem from sample/beamline/data effects.
>>>
>>> --Scott Calvin
>>> Sarah Lawrence College
>>>
>>>
>>> On Nov 5, 2010, at 5:50 PM, María Elena Montero Cabrera wrote:
>>>
>>>  Hello friends,
>>>>
>>>> Hopping someone could help us. We are having some problems in fitting Ru
>>>> K-edge in a Ruthenium-cuprate sample on Artemis, with path functions
>>>> obtained using FEFF 8.4, where we got amplitude values of less than 0.50 for
>>>> Ru-O first shells. We think this value probably is wrong, although there are
>>>> some publications where some oxygen deficiency is studied and recorded as
>>>> true. The ATOMS input data was found to be ok due to the Rietveld analysis
>>>> results told us these are good. The reason we think we may be wrong with
>>>> something during the fitting appeared  because we tried to fit our reference
>>>> sample of RuO2 (measured under same conditions as the experiment of Ru-Cu at
>>>> SSRL) and we came to the same results, even worst, of amplitude lower than
>>>> 0.40. We are attaching the Artemis files so you can take a look on it and
>>>> give us some light to continue with our analysis.
>>>> Thanking in advance, take care
>>>>
>>>
>>>
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>>
>>
>>
>> --
>> María Elena
>>
>> Dra. María Elena Montero Cabrera
>> Centro de Investigación en Materiales Avanzados (CIMAV)
>> Miguel de Cervantes 120, Compl. Ind. Chihuahua
>> Chihuahua CP 31109, Chih. México
>> Tel (614) 4391123
>>
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>>
>
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-- 
María Elena

Dra. María Elena Montero Cabrera
Centro de Investigación en Materiales Avanzados (CIMAV)
Miguel de Cervantes 120, Compl. Ind. Chihuahua
Chihuahua CP 31109, Chih. México
Tel (614) 4391123
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