The hyperfine interactions of fluorine ions in the vicinity of Cr³⁺ and Cr⁺ in KMgF₃. II. Overlap contributions to the second nearest fluorine interaction

For pt.I see ibid., vol.4, 681 (1971). Observed departures from a purely dipolar value for the second nearest fluorine interaction for Cr³⁺ and Cr⁺ in KMgF₃ are discussed in terms of an overlap model. The nondipolar contribution is assumed to be caused by overlap with unpaired spin in the orbits of the intervening first nearest fluorine. To give agreement with experiment, displacements of the first nearest fluorines must be allowed. In the case of Cr³⁺ the displacements are inwards, whilst for Cr⁺ they are outwards. The conclusion is consistent with the charge states of the two ions, which are at divalent sites of the lattice.