ELECTRON PARAMAGNETIC RESONANCE SPECTRA OF Pr4+ IONS DOPED IN PYROCHLORE-TYPE COMPOUNDS La2Sn2O7 AND La2Zr2O7

摘要

The electron paramagnetic resonance spectra of powders with the Pr4+ ions doped in the B sites of the pyrochlore-type compounds A2B2O7 (A=La; B=Sn or Zr) were successfully measured at 4.2 K. A very large hyperfine interaction with the 141Pr nucleus was observed. The spectra were isotropic, which indicates that the symmetry of the O coordination around Pr4+ ions is almost octahedral. The results were analyzed based on the weak field approximation, and the g values and hyperfine coupling constants A were obtained. The measured g values are smaller than |-10/7| (which is calculated for the GAMMA7 ground doublet in the 2F5/2 multiplet), showing that the crystal field is effective to some extent on the behavior of a 4f electron in solids. The value of |g| decreases from 1.270 (Pr4+/La2Zr2O7) to 1.262 (Pr4+/La2Sn2O7), which is caused by the increase of the crystal field due to shrinking of the lattice. On the other hand, the hyperfine coupling constants are the same: A=0.076(1) cm-1. 12 refs.