Heat capacity and thermodynamic functions of new cobaltic manganites $\mathrm{NdM}_2^{\text{II}}\mathrm{CoMnO}_6\,(\text{M}^{\text{II}}$ – $\mathrm{Mg}, \mathrm{Ca}, \mathrm{Sr}, \mathrm{Ba})$ within the temperature range $298.15$–$673$ K

The results of thermodynamic studies of the cobaltic manganites $\rm NdM^{II}_2CoMnO_6\,(M^{II} - Mg, Ca, Sr, Ba)$ are presented. In the calorimetric studies of the heat capacity within the range 298.15–673 K, a second kind $\lambda$-shaped phase transitions in the $C_p(T)$ dependences was discovered: at the temperatures $373$ and $523$ K there is $\rm NdMg_2CoMnO_6$; at $348$ and $498$ K, $\rm NdCa_2CoMnO_6$; at $423$ and $548$ K, $\rm NdSr_2CoMnO_6$; and at $323$ and $498$ K, $\rm NdBa_2CoMnO_6$. We derive the equations for the temperature dependence of the heat capacity with account for these phase transitions. We calculate the temperature dependencies of the thermodynamic functions: entropy, $S^0(T)$, enthalpy, $H^0(T) - H^0(298.15)$, and the reduced thermodynamic potential, $\Phi^{xx}(T)$, of the studied manganites.