Jahn-Teller Type Self-Trapping of Holes in Mixed Crystals AgBr_1−xCl_x

抄録

Electron spin resonance study shows that holes in Cl-rich AgBr_1−xCl_x mixed crystals are self-trapped as the Ag²⁺ complexes having Br ligand ions, (AgBrCl₅)⁴⁻, (AgBr₂Cl₄)⁴⁻ I, II and (AgBr₄Cl₂)⁴⁻ besides (AgCl₆)⁴⁻. The complexes (AgBr₂Cl₄)⁴⁻ II and (AgBr₄Cl₂)⁴⁻ which have two and four Br ligand ions in the same plane respectively have the tetragonal symmetry due to the crystalline field created by Br ions and the Jahn-Teller effect. The anisotropy in g values for these complexes is, however, reduced somewhat compared with that expected by the static Jahn-Teller effect. The decay temperatures of the complexes (AgCl₆)⁴⁻ and (AgBrCl₅)⁴⁻ are decreased with the increase of the concentration of Br ions. This fact is discussed with the theory of optical-phonon-assisted hopping.