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Submitted on 1 Jan 1976
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THE DISTURBANCE SURROUNDING S-P
ELEMENTS OF THE THIRD AND FOURTH PERIOD
DISSOLVED IN IRON
T. Cranshaw
To cite this version:
JOURNAL DE PHYSIQUE Colloque C6, suppl6ment au no 12, Tome 37, De'cembre 1976, page C6-391
THE DISTURBANCE SURROUNDING S-P ELEMENTS
OF THE THIRD AND FOURTH PERIOD DISSOLVED
IN IRON
T. E. CRANSHAW
Nuclear Physics Division, AERE, Harwell, Oxon, England
RBsumB.
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A partir des spectres Mossbauer d'kchantillons monocristallins ayant leurs axes d'aimantations dans les directions [loo] et [Ill], on a dktermink non seulement les variations AHI, AS1, AH2, AS2, des champs hyperfins et du dkplacement isomerique sur les 1"' et 2' voisins, mais aussi les moments dipolaires magnetiques et quadrupolaires klectriques PI, 91, ~ 2 , 92 sur les1"' et 2' voisins ; des considkrations purement gkomktriques permettent d'attribuer sans ambigultk ces dernikres interactions aux couches de voisins appropriees. Une ktude visuelle des spectres, sans recours a une analyse i la machine, montre que, dans les cas de Si, Al, Ga et Ge au moins, un atome de fer ayant un atome de solutk en premier voisin n'a jamais un autre atome de solutk en second voisin. Si I'on considkre seulement les klkments Cu-As, on trouve que AH1, AS1, AH2, AS2, p2, 92, dkpendent pratiquement linkairement de Z et que I'extrapolation de ces grandeurs est zkro pour
Z
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Z N ~ , bien que la precision expkrimentale ne permette pas d'exclure la valeur extrapol&Z
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ZFe. Ceci suggkre que tous ces effets sont dus au micanisme d'kcrantage, les charges a kcranter ktant celles situkes l'extkrieur de la couche.pl et 92 varient de faqon moins systkmatique et sont sans doute sensibles 2 des perturbations dues aux effets de taille.
Abstract,
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Mossbauer spectra of single crystal specimens of alloys taken with the magnetization axis along [loo] and [I 111 permit the determination of not only AHI, AS1, AHz, AS2 the changes in hyperfine field and isomer shift at 1st and 2nd neighbours, but also PI, 91, p2, 92, the magnetic dipole and electric quadrupole interactions at 1st and 2nd neighbours. Purely geometric conside- rations allow unambiguous assignment of these latter interactions to the appropriate neighbour shell. Visual inspection of the spectra, without recourse to computation shows that at least in the cases Si, Al, Ga, Ge, when an iron atom has a first neighbour solute atom, it never has a second neighbour solute atom. Considering only the elements Cu-As, we find that AHI, ASI, AH2, AS2, p2, 92 are a11 nearly linear in Z, and that the extrapoIated vaIue for each of these quantities is zero when Z-
Z N ~ , although experimental errors would not exclude the value Z-
Z F ~ . This suggests that all these effects are caused by the charge screening mechanism, where the charge to be screened is the charge outside the closed a shell.pl and q 1 vary more erratically, and may be affected by size mismatch, etc.