TMPD2SI2 AND YBPD2SI2 - A MOSSBAUER-EFFECT STUDY OF CRYSTAL FIELDS AND INTERMEDIATE VALENCE

We report and compare Mossbauer effect measurements on **1**6**9Tm in TmPd//2Si//2 and on **1**7**0Yb both diluted into the TmPd//2Si//2 and in YbPd//2Si//2. for Tm the data is interpreted in terms of a Tm**3** plus charge state and the crystal field parameters, the magnetic ordering temperature and the paramagnetic relaxation rates are obtained. The results on Yb in both the dilute and concentrated cases show no evdence of any magnetic character. The thermal variation of the quadrupole hyperfine interaction is treated in terms of intermediate valence Yb within the interconfiguration fluctuation model and yields a hybridization width of approximately the same size as the expected total energy splitting of the Yb**3** plus **2F//7/////2 configuration (approximately 100 K). The intermediate valence behavior is observed on Yb in both the dilute and concentrated samples. Theoretical line shapes for a Tm**3** plus ground state non-Kramers doublet whose degeneracy is lifted by the crystal field. This analysis predicts absorption lines at Doppler velocities in excess of plus or minus 100 cm/s.