``Super'' Transferred Hyperfine Interactions for Fe3+ Salts

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Abstract
The experiments of Treves on rare‐earth orthoferrites exhibit a hyperfine field at 57Fe which decreases on going from LaFeO3 through LuFeO3. In this paper we calculate the increase of hyperfine field at 57Fe on going from Fe3+ in dilute oxide to LaFeO3, and find for the overlap part an increase by 51 kG which is about twice as large as the experimental value. We suggest that the overlaps between ligands and inner shells of the magnetic ion are reduced due to a repulsion of closed shells. The observed change of hyperfine field with rare‐earth substitution is qualitatively explained by applying the Slater model of superexchange to the mechanism of ``super'' transferred hyperfine interaction.