Abstract
Mössbauer effect and magnetization measurements were employed in order to study the static and especially the dynamic magnetic properties of the nearly Heisenberg ferromagnet EuO near its Curie temperature,T c=69.2 °K. The critical exponent β of the spontaneous magnetization was determined to be β=0.34±0.02. It was shown that critical slowing down of spin fluctuations takes place nearT c with spin relaxation times between 7×10−11 sec (T=1.01T c) and 1.5×10−1 sec (T=1.03T c). The experimental values of the relaxation time were found to be in satisfactory agreement with theoretically computed ones. Just belowT c the Mössbauer spectra exhibit relaxation effects, which are characteristic for the occurence of critical super-paramagnetism. Investigations of several samples indicated quantitatively, that critical superparamagnetism has its origin in the non ideal composition of the real crystal.
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Auszug aus der von der Fakultät für Allgemeine Wissenschaften der Technischen Universität München genehmigten Dissertation.
Herrn Prof. Dr. R. L. Mössbauer danke ich für die Anregung zu dieser Arbeit und für das Interesse, das er ihr stets entgegenbrachte. Mein besonderer Dank gilt auch den Herren Dr. H. Pink (Siemens AG, München), Dr. O. Vogt (ETH, Zürich), Dr. E. Kaldis und Dipl.-Chem. R. Hauger (ETH, Zürich) und Dr. M. W. Shafer (IBM, Yorktown Heights), die die in dieser Arbeit verwendeten EuO-Proben zur Verfügung stellten.
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Groll, G. Das kritische magnetische Verhalten von EuO. Z. Physik 243, 60–78 (1971). https://doi.org/10.1007/BF01401028
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DOI: https://doi.org/10.1007/BF01401028