Spin–Lattice Coupling Constants of Divalent Manganese in a Tetragonal Lattice

The shift of the fine structure resonances of Mn 2+ in KN 3 due to uniaxial stress are measured and the spin‐lattice Coefficients, C 13 and C 33 are measured t o be 3.53 × 10 −13 and ‐7.06 × 10 −13 cm/dyn respectively. The Blume‐Orbach model and the point ion representation of the lattice potential are used to calculate the zero‐field splitting yielding a value of +395.8 G compared to the experimental value of 534 G measured at room temperature. The theory is also used to calculate the zero‐field splitting as a function of uniaxial stress and spin‐lattice coefficients in excellent agreement with the measured values are obtained. A calculation of the implicit temperature dependence of the zero‐field splitting predicts a linear dependence on temperature with a slope of ‐0.14 G/deg which is markedly smaller than the measured value of ‐0.76 G/deg. The difference is attributed to the fact that the dominant influence in the temperature dependence is a coupling to the lattice vibrations. The effect of the relaxation of the nearest neighbor azide ions about the Mn 2+ on the calculated zero‐field splitting is also considered.