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Exchange and crystal field effects on the 4f n 1 5d levels of Tb 3

2003; IOP Publishing; Volume: 15; Issue: 36 Linguagem: Inglês

10.1088/0953-8984/15/36/313

1361-648X

P. Dorenbos,

Inorganic Fluorides and Related Compounds

The levels of the 4fn−15d configuration of Ce3+(n = 1), Pr3+(n = 2), and Tb3+(n = 8) in compounds are compared with each other. A model is presented that, by means of energy shift operations performed on the five 5d levels of Ce3+, reproduces the energies of those for Pr3+ and Tb3+. Using Tb3+ data, two main sources of deviations from the shift model are identified. One is related to the size difference between Tb3+ and Ce3+ which affects the lattice relaxation and the crystal field splitting of the 5d configuration. The other is related to the isotropic exchange interaction between the 5d electron spin and the total spin of the 4f7 electrons in Tb3+. The exchange splitting is about 1 eV in fluorides, sulfates, and phosphates. In oxides with less strongly bonded oxygen 2p electrons, the exchange splitting decreases to 0.6 eV. The effects of the two deviations on the predictability of the 4fn−15d energy levels of Tb3+ and other lanthanides are discussed.