The calorimetry and thermodynamic functions of $\mathrm{NdMe}^{\mathrm{I}}_3\mathrm{Mg}_3\mathrm{Mn}_4\mathrm{O}_{12}$ $(\mathrm{Me}^{\mathrm{I}} - \mathrm{Li, Na, K})$ manganites in the range from $298.15$ to $673$ K

The ceramic technology is employed for synthesizing manganites of composition $\mathrm{NdMe}^{\mathrm{I}}_3\mathrm{Mg}_3\mathrm{Mn}_4\mathrm{O}_{12}$ $(\mathrm{Me}^{\mathrm{I}} - \mathrm{Li, Na, K})$. The X-ray technique is used to find that the compounds crystallize in tetragonal syngony. The parameters of their crystal lattices are determined. Their heat capacities are experimentally determined in the range from $298.15$ to $673$ K, which enables one to reveal second-order phase transitions. In view of these transitions, equations describing the $C^{\circ}_p \sim f(T)$ dependence are derived, and the thermodynamic functions $C^{\circ}_p(T)$, $H^{\circ}(T) - H^{\circ}(298.15)$, $S^{\circ}(T)$ и $\Phi^{xx}(T)$ are calculated.