Thermophysical properties of manganese monotelluride from 298 to 700 K. Lattice constants, magnetic susceptibility, and antiferromagnetic transition

• Published in: The Journal of chemical thermodynamics 1972-01, Vol.4 (6), p.795-806
• Main Authors: Grønvold, Fredrik, Kveseth, Nils Jørgen, Marques, Fernando Dos Santos, Tichy, Jiri
• Format: Article
• Language: English
• ISSN: 0021-9614
• DOI: 10.1016/0021-9614(72)90001-8

The heat capacity of manganese monotelluride has been determined by adiabatic shield calorimetry in the region 300 to 700 K. A λ-type transition is present with a maximum heat capacity of 83 J K −1 mol −1 at 305 K connected with a change from antiferro-magnetism to paramagnetism in the compound. The heat capacity then decreases to a minimum of 54.4 J K −1 mol −1 at 500 K and reaches 57.1 J K −1 mol −1 at 700 K. Entropies and enthalpies have been calculated and tabulated for selected temperatures. The total increments are: S o(700 K) − S o(298.15 K) = 48.72 J K −1 mol −1 and H o(700 K) − H o(298.15 K) = 22.705 kJ mol −1. In an attempt to analyze the influence of the magnetic contributions, the expansivity of MnTe was determined by X-ray diffraction in the range 300 to 800 K, and the magnetic susceptibility was redetermined. The latter data were interpreted in terms of zero-field splitting of the 6 S 5 2 ground state of the manganese atom with the ± 1 2 components lowest in energy, followed by ± 3 2 at E 1 k = 200 K and ± 5 2 at E 2 k = 1300 K . The magnetic entropy acquired up to 700 K should then be ΔS tr = 13.35 J K −1 mol −1. This value compares well with the value 12.1 J K −1 mol −1 obtained by subtracting the estimated lattice and dilational entropies from the observed value.