Electron–phonon coupling and Jahn–Teller effect in KMgF₃:Cr³⁺

Abstract

Energy levels of the Cr 3+ ion in the KMgF 3 crystal are analyzed by means of the crystal field theory. Electron -phonon coupling constants (the Stokes shift, the force constants and the constants of the linear vibronic Hamiltonian) are evaluated using experimental spectroscopic data. The T e ⊗ Jahn -Teller effect in the lowest excited 4 T 2g state of the Cr 3+ ion is considered using both Ham effect and analysis of the displacements of ligands due to the combined effect of the a 1g and e g normal modes of the [CrF 6 ] 3-octahedral complex. The net result of these vibrations for this cluster is an equatorial expansion by 0.070 Å and an axial compression by 0.008 Å. The value of the Jahn-Teller stabilization energy for the considered complex is about 357 cm -1 .

Jahn-Teller induced nematic orbital order in tetragonalSr2VO4

“…In the present material the spin-orbit parameter is λ = −30 meV [9]. Furthermore, using experimentally-based data for RbMnF 3 [25]) and KMgF 3 [26,27], we obtain V = 3 1/2 V E /2 = −0.26 ± 0.05 eV/Å, and the relevant force constant is k = 2eV/Å 2 . With these parameters the coupling constant v = 1.5 ± 0.5, which is above the critical value v = 1.…”

Electron-phonon Coupling in the 4T2g Excited Electron State of Cs2GeF6:Mn4+

“…It should be pointed out, that similar analyses performed for the Cr 3+ ion in Cs 2 NaYCl 6 :Cr 3+ and Cs 2 NaYBr 6 :Cr 3+ [20,22], Cs 2 NaScCl 6 :Cr 3+ [23] and CsCaF 3 :V 2+ [35] have lead to a deformation of the opposite sign along the z-axis, namely, to a slight axial contraction, whereas for CsCaF 3 :V 2+ [26] and Cs 2 GeF 6 :Mn 4+ we have a slight axial stretching. The criterion, which defines the contraction along the z-axis deformation, is |∆Q a 1g | eq < |∆Q e g | eq √ 2.…”

“…Like in [35], the coordinate system in the (Q θ , Q ε ) space can always be chosen in such a way, that the potential minimum of the 4 T 2g component under consideration (either ξ , η or ζ ) lies on the Q θ axis, i.e. no distortion occurs along Q ε .…”

Dynamic Jahn-Teller effect in crystals doped with 3d ions

“…Evidences for strong JT effect have been found in the Cr 3+ -doped 1) Al 2 O 3 [27], [54], 2) GaAs [55], 3) KMgF 3 [56,57]. The optical spectra of Cr 3+ in fluorides have been theoretically studied in Refs.…”