EPR Study of Cr³⁺–Li⁺ Centres in Several Perovskite Fluorides

Abstract

Centres with tetragonal symmetry in KZnF₃, KCdF₃, RbCdF₃ and CsCdF₃ co-doped with Cr³⁺ and Li⁺ ions have been studied by EPR in the cubic phase of host crystals. Due to charge compensation some of Cr³⁺ ions are associated with a cation vacancy (V_M) or a Li⁺ ion at the nearest divalent-cation site. The magnitude of the fine structure parameter D in the spin Hamiltonian increases with lattice constant for the Cr³⁺–Li⁺ centre. In KZnF₃ the magnitude of D for the Cr³⁺–Li⁺ centre is smaller than that for the Cr³⁺–V_M centre as expected from point charge model, whereas in KCdF₃, RbCdF₃ and CsCdF₃ the former is larger than the latter against the expectation from the point charge model. The dependence of D on lattice constant is discussed.