STUDIES OF THE SPIN-HAMILTONIAN PARAMETERS AND DEFECT STRUCTURES FOR Cu2+ IONS IN AgCl and NaCl CRYSTALS FROM A TWO-MECHANISM MODEL

Abstract

In this paper, based on a two-mechanism model, we derive the complete high-order perturbation formulas of the spin-Hamiltonian (SH) parameters (g factors g‖, g⊥ and hyperfine structure constants A‖, A⊥) for 3d9 ions in tetragonally elongated octahedral clusters. In the model, the contributions to SH parameters due to the crystal-field (CF) mechanism related to CF excited states and the charge-transfer (CT) mechanism related to CT exacted states (the CT mechanism is neglected in CF theory, which is widely used to study the SH parameters) are taken into account. From these formulas, the SH parameters of Cu 2+ ions in AgCl and NaCl crystals are calculated. It is found that for the exact explanation of SH parameters of ( CuCl 6)4- clusters in crystals, the contribution due to CT mechanism should be considered. The relative importance of CT mechanism (characterized by Q CT /Q CF , where Q = Δgi or [Formula: see text], i = ‖ or ⊥) increases with the decreasing metal-ligand distance in ( CuCl 6)4- clusters. The causes are discussed. The signs of Ai and the defect structures of Cu 2+ centers in AgCl and NaCl crystals are suggested from the calculations.