Energy levels and correlation crystal-field effects inEr3+-doped garnets (original) (raw)

The crystal-field energy-level structures of three different Er +-doped garnet systems are analyzed and compared in this study. The garnet hosts are Y,A150» (YAG), Y3Sc2A130» (YSAG) doped with Tm'+ as a sensitizer ion, and Y3Sc2Ga30» (YSGG) doped with Cr as a sensitizer ion. The focus is on energy levels assigned to Er + ions substituted for Y + at dodecahedral (D2 symmetry) sites in the cubic garnet lattices. Analyses are carried out on experimental energy-level data that span up to 29 different +'LJ multiplet manifolds (between 0 and 44000 cm ') of the Er'+ 4f" electronic configuration. These data include the locations of 117 crystal-field levels of Er'+ in YAG, 109 levels of Er'+ in YSAG, and 92 levels of Er'+ in YSGG. The energy-level analyses are based on the use of a parametrized model Hamiltonian for the 4f" electronic configuration of Er'+ in a crystal field of D2 symmetry. The model Hamiltonian includes both atomic ("free-ion") and crystal-field interactions, parametrized to fit calculated eigenvalues to experimentally observed energies. The crystal-field part of the Hamiltonian is defined to include the standard one-electron interaction operators, as well as additional operators that provide a partial, phenomenological consideration of electron-correlation effects in the 4f-electroncrystal-field interactions. The latter, correlation crystal fteld (CCF) interactions, are introduced to address crystal-field splittings within several J-multiplet manifolds that are poorly represented by one-electron crystal-field interaction models. Inclusion of CCF terms in the model Hamiltonian leads to dramatic improvement in the fits between calculated and observed crystal-field splittings within the problematic multiplet manifolds. All of the energy-level analyses reported in this study were carried out within commensurate parametrization schemes, and the Hamiltonian parameters derived from these analyses provide a suitable basis for comparing the 4f-electroncrystal-field interaction properties of Er + in YACC, YSAG, and YSGG. These analyses are based entirely on experimental data that specify the locations of energy levels, but do not provide any explicit information about the angular momentum (JMJ) compositions of the crystal-field wave functions. energy levels assigned to Er + ions substituted for Y + at dodecahedral (Dz symmetry) sites in the cubic garnet lat-0163-1829/93/48(21)/15561(13)/$06. 00 48 15 561 1993 The American Physical Society 1S 562 JOHN B. GRUBER et aI. 48 tices. The main emphasis is on comparative energy-level analyses that rellect differences (and similarities) between Er + (4f ") host-lattice interactions in the respective systems. The energy-level data included in our analyses span 29 +'L~(4f ") multiplet manifolds of Er + in YAG and YSAG, and 22 multiplet manifolds of Er + in YSGG. These data include the locations of 117 crystalfield levels of Er + in YAG, 109 levels of Er + in YSAG, and 92 levels of Er in YSGG. All of these crystal-field levels are Kramers doublets of identical symmetry (E,&2) in the D2 double group. The experimental data analyzed in this study provide information about the energies of the crystal-field levels, but they do not provide explicit information about the angular momentum (JMz) properties of these levels. Our energy-level analyses are based on the use of a parametrized model Hamiltonian for the 4f" electronic