Study of Fluorine Hyperfine Interactions in KZnF 3 : V 2+ and Cr 3+ by ENDOR

Fluorine ENDOR measurements have been made on first and second fluorine neighbours to V 2+ and Cr 3+ in KZnF 3 in order to clarify the role of the intervening Zn 2+ ions. The isotropic hf interaction parameters for the second fluorine neighbours have been obtained as +79 kHz and -22 kHz for v 2+ and Cr 3+ respectively. The negative sign of the result for the Cr 3+ strongly suggests that the cation-cation charge transfer interaction between the 3d 3 impurity and Zn 2+ ions can play important roles in these systems. Differences between the KMgF 3 and KZnF 3 for both V 2+ and Cr 3+ are discussed from the same standpoint.