Abstract:The 5 D terms of Fe 2+ and Cr 2+ in the tetrahedral potential at cation sites in II-VI compounds split into orbital doublet and triplet states. While in Cr 2+ the orbital triplet has lower energy than the doublet, the opposite is the case in Fe 2+ . Both ions have singlet ground states after the spin-orbit interaction is taken into account and, hence, both are Van Vleck paramagnets. The optical absorption spectra of Fe and Cr based materials differ and are explained on the basis of a dynamic Jahn-Teller effec… Show more
“…For the Jahn-Teller energies three different parameters are necessary, in agreement with Vallin et al 27 In Vallins case the Jahn-Teller energy is larger, the Cr 2ϩ displacement in the host lattice will be larger, and to obtain the same energy level scheme the spin-orbit interaction parameters must increase as well to account for the smaller overlap between the Cr 2ϩ 3d wave functions and the ligand wave 24 we used slightly higher crystal field parameters, but neglected the spin-spin interaction term in the Hamiltonian and diversified the spin-orbit parameter, where Colignon used a too general approach, using the free ion spin-orbit parameter value. They also find a large difference in the Jahn-Teller energy values over the three compounds, while we used approximately the same values for all three host lattices.…”
Section: Comparisonmentioning
confidence: 75%
“…where, instead of using one free ion spin-orbit coupling parameter, 24 we used three different parameters. This reflects the fact that the strength of the spin-orbit coupling may depend on admixture between the Cr 3d wave functions and the ligand wave functions, which is different for the 5 E and 5 T 2 states.…”
We have studied magnetic interactions in chromium-based diluted magnetic semiconductors by measuring in detail the electron paramagnetic resonance spectrum of Cr 2ϩ over the frequency range between 30 and 210 GHz at high magnetic fields up to 20 T oriented along different crystal axes. At low temperatures, crystals of chromium-alloyed zinc chalcogenides Zn 1Ϫx Cr x ͑S, Se, Te͒ demonstrate complex properties that are neither of Brillouin nor of Van Vleck type. The behavior of these Cr 2ϩ impurities in semimagnetic materials results from the interaction of the ground state with the low-lying electronic states of the 3d Cr 2ϩ ion and from the Jahn-Teller-induced distortion of the Cr 2ϩ position in the host lattice. We measured optical transitions between these states and we could determine the magnetic-field dependence and the anisotropy of the electronic levels. We explain our results with the crystal-field model proposed by Vallin et al., 1 including a cubic crystal field and Jahn-Teller distortion, and we evaluate the dependence of the model parameters on the semiconductor host lattice.
“…For the Jahn-Teller energies three different parameters are necessary, in agreement with Vallin et al 27 In Vallins case the Jahn-Teller energy is larger, the Cr 2ϩ displacement in the host lattice will be larger, and to obtain the same energy level scheme the spin-orbit interaction parameters must increase as well to account for the smaller overlap between the Cr 2ϩ 3d wave functions and the ligand wave 24 we used slightly higher crystal field parameters, but neglected the spin-spin interaction term in the Hamiltonian and diversified the spin-orbit parameter, where Colignon used a too general approach, using the free ion spin-orbit parameter value. They also find a large difference in the Jahn-Teller energy values over the three compounds, while we used approximately the same values for all three host lattices.…”
Section: Comparisonmentioning
confidence: 75%
“…where, instead of using one free ion spin-orbit coupling parameter, 24 we used three different parameters. This reflects the fact that the strength of the spin-orbit coupling may depend on admixture between the Cr 3d wave functions and the ligand wave functions, which is different for the 5 E and 5 T 2 states.…”
We have studied magnetic interactions in chromium-based diluted magnetic semiconductors by measuring in detail the electron paramagnetic resonance spectrum of Cr 2ϩ over the frequency range between 30 and 210 GHz at high magnetic fields up to 20 T oriented along different crystal axes. At low temperatures, crystals of chromium-alloyed zinc chalcogenides Zn 1Ϫx Cr x ͑S, Se, Te͒ demonstrate complex properties that are neither of Brillouin nor of Van Vleck type. The behavior of these Cr 2ϩ impurities in semimagnetic materials results from the interaction of the ground state with the low-lying electronic states of the 3d Cr 2ϩ ion and from the Jahn-Teller-induced distortion of the Cr 2ϩ position in the host lattice. We measured optical transitions between these states and we could determine the magnetic-field dependence and the anisotropy of the electronic levels. We explain our results with the crystal-field model proposed by Vallin et al., 1 including a cubic crystal field and Jahn-Teller distortion, and we evaluate the dependence of the model parameters on the semiconductor host lattice.
“…The importance of the JT effect on the specific heat and magnetic properties of these systems was acknowledged and some possible coupling mechanisms and competing distortions have been subsequently suggested [82]. More recently, higher resolution luminescence spectra and well resolved absorption experiments were added to information of the infrared properties of Cr 2+ in semiconductors [83][84][85].…”
This chapter is devoted to the study of the dynamic Jahn-Teller effect on the optical spectra of 3d-ions impurities in crystals, with particular attention to the theoretical efforts addressed to the interpretation of the experimental results. The presentation assumes that the reader is familiar with the spectroscopic notation for atomic energy levels. In addition, basic concepts and notation of point-group theory are also used. First, we will present a survey of the main experimental and theoretical results according to the electronic configuration. Then we discuss with a tutorial style the main contributions needed to model the optical spectra of the Jahn-Teller active 3d-ions impurities and asimple example is discussed in details. Next we concentrate on the calculation procedures required to address realistic systems. Some applicative examples of the proposed procedure are described in details.
“…II-VI compounds are frequently studied materials because of their multiple applications [1], but it remains still to research the detailed nature of the electronic properties associated with the transition-metal ions doped in such host materials. Most studies [2][3][4][5][6][7][8][9][10][11][12] reveals that these properties can be better explained if were taken into account beside the electrostatic interactions, the Jahn-Teller effect, spin-orbit, spin-spin interactions and Tress correction between the nd electrons of the transition-metal ions doped in semiconductors and between the ions and the ligands. The tetrahedral site symmetry of the impurity Cr 2+ ion doped in ZnS host matrix decrees, due to the static Jahn-Teller effect [2-6], from tetrahedral (T d ) to tetragonal (D 2d ) symmetry, and gives the degeneracy of the energy levels [7,8].…”
Section: Introductionmentioning
confidence: 99%
“…Most studies [2][3][4][5][6][7][8][9][10][11][12] reveals that these properties can be better explained if were taken into account beside the electrostatic interactions, the Jahn-Teller effect, spin-orbit, spin-spin interactions and Tress correction between the nd electrons of the transition-metal ions doped in semiconductors and between the ions and the ligands. The tetrahedral site symmetry of the impurity Cr 2+ ion doped in ZnS host matrix decrees, due to the static Jahn-Teller effect [2-6], from tetrahedral (T d ) to tetragonal (D 2d ) symmetry, and gives the degeneracy of the energy levels [7,8]. The spin-orbit, spin-spin interactions and Tress correction also influence the optical and magnetic properties of the Cr 2+ :ZnS system.…”
C 12 H 22 CdN4O14, triclinic, P¯ (no. 2), a = 7.188(2) Å, b = 8.895(3) Å, c = 9.771(3) Å, α = 63.148(3)°, β = 76.750(3)°, γ = 66.225(3)°, V = 509.2(3) Å 3 , Z = 1, Rgt(F) = 0.0253, wR ref (F 2 ) = 0.0676, T = 296(2) K.
CCDC no.: 1484775The crystal structure is shown in the gure. Tables 1 and 2 contain details of the measurement method and a list of the atoms including atomic coordinates and displacement parameters.
Source of materialThe title compound was synthesized by a hydrothermal method under autogenous pressure. A mixture of CdCl 2 ·H 2 O
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