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The influence of aluminium substitution and crystallinity on the Mössbauer spectra of goethite

Published online by Cambridge University Press:  09 July 2018

E. Murad
Affiliation:
Lehrstuhl für Bodenkunde, TU München, D-8050 Freising-Weihenstephan, FRG
U. Schwertmann
Affiliation:
Lehrstuhl für Bodenkunde, TU München, D-8050 Freising-Weihenstephan, FRG

Abstract

Both aluminium substitution and poor crystallinity reduce the magnetic hyperfine field of goethite. Mössbauer spectra taken at 4·2 K show that the effect of poor crystallinity is similar to that of Al substitution, i.e. it reduces the saturation hyperfine field. A multiple correlation was found to exist between the magnetic hyperfine field at 4·2 K as a dependent variable vs Al substitution and crystallinity as independent variables. If a hyperfine field is to be interpreted with respect to either Al substitution or crystallinity, it is therefore necessary to have knowledge of the other variable.

Resume

Resume

Des substitutions par l'aluminium et une mauvaise cristallinité réduisent toutes les deux le champ magnétique hyper-fin de la goethite. Des spectres Mössbauer enregistrés à 4·2 K montrent que l'effet d'une mauvaise cristallinité est semblable à celui de la substitution par Al, c'est-à-dire qu'elle réduit la saturation du champ hyper-fin. On a montré qu'il existe une corrélation multiple entre le champ magnétique hyper-fin à 4·2 K qui admet comme variable dépendante la substitution par Al et le degré de cristallinité en tant que variable indépendante. Si on doit interpréter le champ hyperfin par rapport à la substitution Al ou la cristallinité, il est donc nécessaire de connaître l'une ou l'autre des deux variables.

Kurzreferat

Kurzreferat

Sowohl Al-Substitution als auch geringe Kristallqualität verkleinern das magnetische Hyperfeinfeld von Goethit. Mößbauerspektren bei 4·2 K zeigen, daß der Effekt geringer Kristallqualität ähnlich dem von Al-Substitution ist, also das Sättigungshyperfeinfeld verringert. Zwischen dem magnetischen Hyperfeinfeld bei 4·2 K (als Zielgröße) und der Al-Substitution und der Kristallinität (als unabhängige Variablen) wurde eine multiple Korrelation gefunden. Bevor ein Hyperfeinfeld im Hinblick auf Al-Substitution oder Kristallqualität interpretiert wird, ist es daher notwendig, auch die Größe der jeweils anderen Variablen zu kennen.

Resumen

Resumen

Tanto la sustitución de hierro por aluminio como la baja cristalinidad reducen el campo magnético hiperfino de la goethita. Los espectros Mössbauer obtenidos a 4·2 K muestran que el efecto de la baja cristalinidad es similar al de la sustitución de aluminio, es decir reduce el campo hiperfino de saturación. Se encontró que existe una correlación múltiple entre el campo magnético hiperfino a 4·2 K como variable dependiente y la sustitución de aluminio y la cristalinidad como variables independientes. Por lo tanto, para interpretar los valores del campo hiperfino es necesario tener en cuenta las dos variables citadas.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1983

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