Spectroscopic properties of single crystals of rare earth titanates

Effects of distortions in ion-host systems on optical spectra, crystal-field and spin-Hamiltonian parameters of Cr3+ ions doped pyrochlores Y2Ti2O7 and Y2Sn2O7: exchange charge model and superposition model calculations

“…The calculated CF energies are listed in Table 3: in column (f) – matching with the experimental 37,40 energies in column (h) for Y 2 Ti 2 O 7 :Cr 3+ . The ZFS of the ground orbital singlet 4 A 2g state is 1.908 cm −1 .…”

“…The ECM/CFPs for Cr 3+ ions in the Y 2 Ti 2 O 7 host were calculated using the parameter G (see, Table 3) adjusted by matching the computed energies with the experimental ones. 37,40 The Racah parameters, B = 762.5 cm −1 and C = 2877 cm −1 , were reduced from the Cr 3+ free-ion value of B 0 = 1030 cm −1 and C 0 = 3850 cm −1 , 48,55 due to the nephelauxetic effect 48 and the low site symmetry effect. 18 The nephelauxetic ratio: β 1 = is 1.052.…”

“…35 The ECM/CFPs are evaluated using ECM overlapping parameters: G s , G σ , and G π ; whereas the SPM/CFPs are determined by four fitting parameters: Ā 2 , Ā 4 , and t 2 , t 4 . However, these two sets of model parameters were adjusted independently from the best fits of the calculated energy levels to the experimental spectra of Cr 3+ ions doped in Y 2 Ti 2 O 7 37,40 and Y 2 Sn 2 O 7 . 38 The calculated ECM/CFPs and SPM/CFPs, as well as Racah parameters, B and C , SOC parameter ζ so , and M 0 and M 2 are treated as the input for diagonalization of Hamiltonian (1) for the CFA/MSH program, 7 a , b ,11,17 and hence the energy levels are calculated.…”

“…Including these distortions, eqn (11), yields explicit expressions for SPM/CFPs as:To consider the effects of these dopant-induced distortions, the SPM/CFPs were calculated by varying four parameters: Ā 2 , Ā 4 , Δ R and Δ θ , by matching the computed SHPs and energy levels of Cr 3+ ions with the available experimental data. 37,40 The power-law exponents, t k , were taken equal to k + 1 as predicted by the point charge model, 29,33 i.e. , t 2 = 3 and t 4 = 5.…”

Optical Observation of Striations in Y2Ti2O7 Single Crystals

“…Pyrochlore oxides of the composition RE 2 Ti 2 O 7 have a face-centered cubic crystal structure with the space group Fd-3m (227), in which RE and Ti sit on the centers of octahedron and dodecahedron O atoms in the oxygen sub-lattice. RE ions or Ti ions can be substituted by transition-metals (TM), such as Cr, Co, and Mn, and TM-doped RE 2 Ti 2 O 7 crystals can be obtained [11][12][13][14][15]. The energy levels of TM ions can be split by the crystal fields of the O-octahedra and the O-dodecahedra in the RE 2 Ti 2 O 7 crystals.…”