The specific heat of N(CH3)4MnBr3by adiabatic calorimetry

The specific heat of N(CH 3 ) 4 MnBr 3 has been measured by adiabatic calorimetry, using both static and dynamic methods. The obtained results have permitted the calorimetric characterization of the phase transition which the crystal shows at 143 K. The comparison with other compounds of the family has been used to generate an adequate baseline for the normal lattice contribution to the specific heat. These results allow for an accurate estimation of the phase transition thermodynamic functions: ΔH = 218 R K and ΔS = 1.58 R. The calorimetric data are very close to those found for the isomorphous N(CH 3 ) 4 CdBr 3 and suggest a similar frequency spectrum for the lattice vibrational modes and the anharmonic contributions to the specific heat.