Electron Paramagnetic Resonance Spectra of Pr4+Ions Doped in Pyrochlore-Type Compounds La2Sn2O7and La2Zr2O7

The electron paramagnetic resonance spectra of powders with the Pr4+ions doped in the B sites of the pyrochlore-type compoundsA2B2O7(A=La;B=Sn or Zr) were successfully measured at 4.2 K. A very large hyperfine interaction with the141Pr nucleus was observed. The spectra were isotropic, which indicates that the symmetry of the oxygen coordination around Pr4 +ions is almost octahedral. The results were analyzed based on the weak field approximation, and thegvalues and hyperfine coupling constantsAwere obtained. The measuredgvalues are smaller than -10/7 (which is calculated for the 7ground doublet in the2F5/2multiplet), showing that the crystal field is effective to some extent on the behavior of a 4felectron 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.