EPR of Mn²⁺ in CdGa₂S₄ and in CdGa₂Se₄ ; Influence of Covalent Bonding on the Parameters of the Spin-Hamiltonian

Abstract

Abstract The EPR-spectra of Mn 2+ in CdGa 2 X 4 (X = S, Se) single crystals were measured and described by a Spin-Hamiltonian with an axial and with a cubic crystal field component: D=-(225.3±0.2)·10 -4 cm -1 and a= (6.6 ± 0.2)·10 -4 cm -1 for CdGa 2 S 4 ; D=-(919.3±0.3)·10 -4 cm -1 and a= (15 ± 2)·10 -4 cm -1 for CdGa 2 Se 4 . The g-values g ∥ = 2.0012 ± 0.0005, g ⊥ = 2.0016 ± 0.0010 for CdGa 2 S 4 and g ∥ = 2.0029 ± 0.0005, g ⊥= 2.0039 + 0.0010 for CdGa 2 Se 4 are slightly different from those of the binary chalcogenides CdX (X = S, Se). The hyperfine constants A, - (64.0 ± 0.3)·10 -4 cm -1 for CdGa 2 S 4 and - (60.7 ±0.3)·10 -4 cm -1 for CdGa 2 Se 4 are nearly the same as those of the equivalent binary cadmium chalcogenides. It is shown that all parameters of the cadmium chalcogenides are characterized by the covalent part of the bonding. The g-values can be explained by an interaction of the 3d orbitals of Mn 2+ with the ligand orbitals. The hyperfine constant is caused by an interaction of the excited 4s-Mn 2+ states with the ligand states. By optical absorption measurements the value of the band gap in CdGa 2 X 4 (X = S, Se, Te) is determined.