25 K PHASE TRANSITION IN NPO-2 FROM 237-NP MOESSBAUER SPECTROSCOPY
237-Np Moessbauer spectroscopy in magnetic external fields up to 8 T and in the temperature range 1.5-160 K, demonstrates that NpO-2 remains paramagnetic well below T-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-2 is prevented (or at least depressed) by this competitive structural transition.
Bibliographic Reference: PHYSICAL REVIEW B, VOL. 32 (1985), NO. 1, PP. 257-263
Record Number: 1989124089500 / Last updated on: 1987-01-01
Available languages: en