Das kritische magnetische Verhalten von EuO |
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Authors: | Günter Groll |
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Institution: | 1. Physik-Department der Technischen Universit?t München, Deutschland
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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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