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Abstract
Temperature dependencies of the specific heat in a temperature range of 14–260 K are presented for the crystals (TEA)2MnCl4. Two anomalies typical for the first order phase transition at T 1 = 224 K and T 2 = 231 K with entropy jumps of 15 J mol−1 K−1 and 12 J mol−1 K−1 were observed. The temperature dependence of the lattice heat was approximated by a linear combination of Debye and Einstein functions. Basing on the results an effective wave number of phonons with an essential contribution to the lattice oscillation energy was determined. Since phase transition sequence observed in (TEA)2MnCl4 and (TEA)2CuCl4 is similar and similar is the chemical composition one can suppose that the low temperature phase transition observed in (TEA)2MnCl4 crystals is an isostructural transition.