| Numéro |
J. Phys. Colloques
Volume 40, Numéro C2, Mars 1979
International Conference on The Applications of The Mössbauer Effect
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| Page(s) | C2-676 - C2-676 | |
| DOI | https://doi.org/10.1051/jphyscol:19792234 | |
J. Phys. Colloques 40 (1979) C2-676-C2-676
DOI: 10.1051/jphyscol:19792234
THE LAMB-MÖSSBAUER FACTOR OF METAL IRON FOILS AT 4.2K
H. Vogel, H. Spiering, W. Irler, U. Volland and G. RitterPhysikalisches Institut der Universität Erlanger-Nürnberg, B.D.R.
Résumé
Le facteur Lamb -Mössbauer f est déterminé pour le fer metallique à 4.2K. La méthode consiste à utiliser trois feuilles d'épaisseurs effectives différentes et à mesurer le rapport des surfaces des pics en présence d'un champ magnétique perpendiculaire ou parallel aux feuilles. On obtient ainsi fFE (4,2K) = 0,93 ± 0,03.
Abstract
Recently J.P. Williams and J.S. Brooks /1/ published a novel method of determining the Lamb-Mössbauer factor f of the absorbers. The idea is to get further linear independent equations for f by changing the effective thickness of the same absorber when the polarization of the absorption lines is changed in external magnetic fields . This has been demonstrated on iron foils . They obtained fFe =0.73 at 4.2 K in strong contradiction to fFe=0.92 /2/ calculated from the Debye model with θD=400 K, which has been obtained from the relativistic temperature shift and the resonant absorption in the range 4.2 K-700 K /3/. To our feeling the evaluation in /1/ had to be improved to justify the small fFe(4.2 K) value. We measured three iron foils a t 4.2 K (8.71, 2x8.71, 20 .00 mg Fe/cm2) in large external magnetic fields parallel and normal to the foil . Each foil gives one area ratio for the four line and two for the six line pattern. The ratios yield the value fFe(4.2 K)=0.94±0.04. To obtain this result the non Lorentzian shape of the absorption lines of the thick absorbers, the overlap, and the apparative broadening of our Mössbauer spectrometer have been taken into account. From the thickness dependence of the total areas the fFe factor could not be closely confined. Therefore we determined the fS factor of the source (90 mCi in Rh) by the absorption area of sodium nitroprusside (SNP). With the powder value fSNP(296 K)=0.359 of Grant et al . /4/ for SNP the f factor become fS(306 K)=0.77 anf fFe(4.2 K)=0.83±0.03. We fitted the Debye model to our measurements of the total absorption area of SNP in the range 13 K-300 K and found fSNP(296 K)=0.394. This value results in fS (306 K)=0.72 and fFe(4.2 K)=0.93±0.03 which is in agreement with the value from the area ratios and from /2/.