Electron paramagnetic resonance of Ce3+ in La(CF3SO3)3·9H2O (US)

The rare-earth trifluoromethanesulfonates R(CF3SO3)3·9H2O (RTFMS) have a hexagonal structure similar to the ethylsulfates R(C2H5SO4)3·9H2O (RES). The lowest Kramers doublet in CeTFMS is |J=5/2; Jz = ±5/2 right-angle separated from an excited doublet |J=5/2; Jz= ±1/2 right-angle by Δ/k congruent 21 K. We have measured electron paramagnetic resonance on 1% and 2% Ce3+ in LaTFMS crystals at 9.214 GHz. At 4.2 K, absorption by two doublets is found yielding gparallel(5/2) = 3.813 ± 0.001; gperpendicular(5/2) = 0.262 ± 0.002; gparallel(1/2) = 0.977 ± 0.003; gperpendicular(1/2) = 2.151 ± 0.002. The temperature variation of intensities shows the ground doublet to be |±5/2 right-angle, as in concentrated CeTFMS, but Δ/k=9.6±0.7 K. The doublet order is opposite to that for dilute Ce:LaES but the same as in CeES or Ce:YES and Ce:EuES. In 2% Ce:LaTFMS, satellite resonances due to coupled nn Ce--Ce pairs are also observed. Analysis of the pair data indicates that virtual phonon exchange, while the dominant nondipolar contribution to intrapair coupling, is smaller than for Ce pairs in CeES. This is consistent with the fact that Δ is larger in CeTFMS or Ce:LaTFMS than in CeES