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25-K phase transition in NpO/sub 2/ from /sup 237/Np Moessbauer spectroscopy

Journal Article · · Phys. Rev. B: Condens. Matter; (United States)
/sup 237/Np Moessbauer spectroscopy in magnetic external fields up to 8 T and in the temperature range 1.5--160 K, demonstrates that NpO/sub 2/ remains paramagnetic well below T/sub c/ = 25 K. The specific-heat anomaly, the cusp in magnetic susceptibility, and the changes in the shape of the Moessbauer spectra observed at 25 K are attributed to a structural transition. Both the bulk susceptibility and the Moessbauer data can be satisfactorily reproduced under the assumption of an inhomogeneous compressional-expansional internal distortion of the oxygen sublattice. It is suggested that a magnetic ordering of NpO/sub 2/ is prevented (or at least depressed) by this competitive structural transition.
Research Organization:
Centre de Recherches Nucleaires, 67037 Strasbourg Cedex, France
OSTI ID:
5625644
Journal Information:
Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 32:1; ISSN PRBMD
Country of Publication:
United States
Language:
English