Manganese Disulfide (Hauerite) and Manganese Ditelluride. Thermal Properties from 5 to 350°K and Antiferromagnetic Transitions

The heat capacities of manganese disulfide and manganese ditelluride were determined by adiabatic calorimetry in the range 5–350°K. Lambda‐type transitions are present in both compounds with maxima at 47.93°K for MnS₂ and at 83.0°K for MnTe₂. Entropies, enthalpies, and Gibbs energy function values are calculated and tabulated. At 298.15°K they are: $\text{S°\hspace{0.17em}=\hspace{0.17em}23.88}\mathrm{cal}/\mathrm{mole}\mathrm{·°}\mathrm{K}{\mathrm{,\; H°\hspace{0.17em}-\hspace{0.17em}H}}_0\text{°\hspace{0.17em}=\hspace{0.17em}3384}\mathrm{cal}/\mathrm{mole}{\mathrm{,\; -\hspace{0.17em}[(G°\hspace{0.17em}-\hspace{0.17em}H}}_0\text{°)\hspace{0.17em}/\hspace{0.17em}T]\hspace{0.17em}=\hspace{0.17em}12.258}\mathrm{cal}/\mathrm{mole}\mathrm{·°}\mathrm{K}$ for MnS₂ and 34.66, 4416, and 19.847 for MnTe₂. The clearly cooperative entropy increments are only 0.71 cal/mole·°K for MnS₂ and 0.80 for MnTe₂. Available magnetic susceptibility data are interpreted in terms of zero‐field splitting of the ${}^6{S}_{\text{5/2}}$ state of the manganese ${\text{3d}}^5$ electrons. The resulting contributions to the heat capacity are evaluated. At 298°K the combined λ‐transitional and Schottky contributions to the entropy are 2.6 and 2.4 cal/mole·°K for MnS₂ and MnTe₂, respectively.