Actinide Mossbauer studies

The situation with respect to high-pressure Mossbauer experiments is discussed in section 5. General systematics within the most thoroughly studied series of intermetallics are presented in sectii n6. Section 7 briefly highlights the spin-glass behavior of a class of lanthanide and actinide intermetallics. 

On the other hand. Gal et al. (1990) have shown that the actinide-containing compounds AnFc4Al8 (An = Th, U, Np) are all spin glasses. The so-called spin-glass temperatures, T, where hysteretic and irreversible effects in the magnetization occur, are all about 120 K for these materials. Neutron diffraction (and Mossbauer also, in the case of the Np compound) experiments show that a moment exists on the U and Np sites, but it is not clear from these studies on polycrystalline samples whether the moment directions are random or uniaxial. The dominant spin-glass behavior is, of course, provided by the Fe sublattice. This is not only shown by the various measurements, but also by the fact that Tsg is much the same for the Th compound (no 5f moments exist on the Th) as for the other actinide compounds. 

The importance of Mossbauer spectroscopy in probing electronic structures of intermetallic compounds, especially those reflected in the magnetic properties, is discussed by W. Potzel, G.M. Kalvius and J. Gal (chapter 116). The authors have focused their discussions on selected samples where the differences between lanthanides and actinides can be best contracted. As the authors note, the two most interesting elements, at least with respect to anomalous f-electron behaviors, Ce and U, cannot be studied by Mossbauer spectroscopy because of the lack of a suitable isotope in the case of Ce, and just the experimental difficulty in getting Mossbauer spectra for U. 

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