Optical Absorption, Fluorescence, and Electron Spin Resonance of Ir⁴⁺ on Octahedral Sites in Y₃Ga₅O₁₂

Abstract

Ir4+, incorporated on the octahedral a-sites of Y3Ga50,,:Ir, has been investigated by electron spin resonance a t 9 and 35 GHz, and by optical absorption spectroscopy in the range 5000 to 6000 cm-l. For an unequivocal optical identification Zeeman measurements were performed. I n t h e same energy range fluorescence from Ir4+ could be observed. Analysis of the data obtained b y electron spin resonance and optical techniques reveals that the properties of the ,Tzg ground state of Ir4+ are partly determined by interaction with higher excited states.

Anisotropic magnetic couplings and structure-driven canted to collinear transitions inSr2IrO4by magnetically constrained noncollinear DFT

“…By fitting the U to the experimental bandgap (≈ 0.3 eV [17]) for Ω = 1 we obtain an optimal U of 1.6 eV, similar to the constrained random phase approximation estimation, 1.96 eV [19]. From the total energy difference with and without the inclusion of SOC we have estimated a SOC energy ξ soc of 0.7 eV/Ir, in line with electron spin resonance measurements [38], which is only about half of the computed value of U. These results provide clear evidence for the relativistic Mott-Hubbard character of the insulating state in Sr 2 IrO 4 .…”

Theoretical studies of the spin-Hamiltonian parameters and their stress dependences for Ru3+ and Ir4+ ions in Y3Ga5O12 crystals

“…So, the defect natures and defect structures of TM ions in garnets attract much attention. Since the EPR spectra of TM ions in crystals are sensitive to their immediate environments and hence to the defect natures and structures, many EPR investigations have been made for TM ions in garnets [1,3,[5][6][7][8][9][10][11][12]. Among them, the EPR studies for the 3d n TM ions are much more than those for the 4d n and 5d n ions in garnets.…”

“…Among them, the EPR studies for the 3d n TM ions are much more than those for the 4d n and 5d n ions in garnets. About 30 years ago, the EPR spectra of 4d 5 ion Ru 3+ and 5d 5 ion Ir 4+ in Y 3 Ga 5 O 12 (YGG) garnets were measured [10,11], and the spin-Hamiltonian (SH) parameters (g factors g || , g ⊥ and hyperfine structure constants A || , A ⊥ ) and the stress dependence of g factor g ⊥ for the two d 5 ions in YGG were reported [10][11][12]. md 5 (m = 3, 4 and 5) ions in YGG can occupy the octahedral site with the trigonal symmetry [10][11][12].…”

“…About 30 years ago, the EPR spectra of 4d 5 ion Ru 3+ and 5d 5 ion Ir 4+ in Y 3 Ga 5 O 12 (YGG) garnets were measured [10,11], and the spin-Hamiltonian (SH) parameters (g factors g || , g ⊥ and hyperfine structure constants A || , A ⊥ ) and the stress dependence of g factor g ⊥ for the two d 5 ions in YGG were reported [10][11][12]. md 5 (m = 3, 4 and 5) ions in YGG can occupy the octahedral site with the trigonal symmetry [10][11][12]. Differing from 3d 5 ions (e.g., Mn 2+ and Fe 3+ ) in garnets which belong to the high-spin (S = 5/2) weak-field configuration (where Dq/B < 2.8) [5,13], the Ru 3+ and Ir 4+ ions in garnets are in the low-spin (S = 1/2) strong-field configuration (where the ground state is 2 T 2 ) because of the large cubic field parameter Dq and hence Dq/B > 2.8 [10][11][12][13].…”

“…md 5 (m = 3, 4 and 5) ions in YGG can occupy the octahedral site with the trigonal symmetry [10][11][12]. Differing from 3d 5 ions (e.g., Mn 2+ and Fe 3+ ) in garnets which belong to the high-spin (S = 5/2) weak-field configuration (where Dq/B < 2.8) [5,13], the Ru 3+ and Ir 4+ ions in garnets are in the low-spin (S = 1/2) strong-field configuration (where the ground state is 2 T 2 ) because of the large cubic field parameter Dq and hence Dq/B > 2.8 [10][11][12][13]. Until now no satisfactory and reasonable investigations related to the local structures and the local properties (e.g., local angular compressibility) for the SH parameters and their stress dependences have been made for the Ru 3+ and Ir 4+ impurity centers in YGG.…”