Abstract
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: S° = 23.88 cal/mole·°K, H° − H0° = 3384 cal/mole, − [(G° − H0°) / T] = 12.258 cal/mole·°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 S5/26 state of the manganese 3d5 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.
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