Specific heat capacity of ternary molybdenum sulfides. I. Lattice and electron contributions to the specific heat capacity of superconducting Mo5SnS6 at 2--25 K

The specific heat has been investigated for ternary molybdenum sulfide Mo5SnS6 in the temperature range 2--25 K. To diminish the critical temperature of this compound, a small amount of iron was introduced. Thus it was possible to observe the specific heat in the normal state up to 2 K. From the results of the measurements it follows that the lattice contribution to the specific heat must be described by a linear combination of the usual Debye and an Einstein function. In agreement with the results of Moessbauer effect measurements, the Einstein contribution to the lattice specific heat seems connected with the Sn atoms. On the basis of such a lattice contribution, the γ coefficient of the electronic specific heat has been determined. With increasing iron content a small rise of the γ coefficient is observed