Exchange Contribution to the D-Parameter of Mn²⁺ in CoCl₂·2H₂O

Abstract

The D-value of Mn²⁺ in CoCl₂·2H₂O has been obtained to be −0.13 cm⁻¹ by Date and Motokawa. The large negative D value is reasonably explained by introducing an effective exchange interaction of general form between the Mn²⁺ and the ground Kramers doublet of Co²⁺, taking account of the crystal symmetry. It is shown that the interaction −2J^xzs_xS_z −2J^yzs_yS_z is responsible for the negative D-parameter. The effective exchange interaction is derived from the nondiagonal exchange between Mn²⁺ and Co²⁺ with respect to the cobaltous orbits by projecting the exchange to the ground Kramers doublet.