Heat Capacity and Thermodynamic Functions of New Cobaltic Manganites (MII is Mg, Ca, Sr, or Ba) Within the Temperature Range of 298.15–673 K

Abstract

The results of thermodynamic studies of the cobaltic manganites (MII is Mg, Ca, Sr, or Ba) are presented. In the calorimetric studies of the heat capacity within the range of 298.15–673 K, a second kind λ-shaped phase transitions in the Cp(T) dependences was discovered: at the temperatures of 373 and 523 K for NdMg2CoMnO6; at 348 and 498 K for NdCa2CoMnO6; at 423 and 548 K for NdSr2CoMnO6; and at 323 and 498 K for NdBa2CoMnO6. We derive the equations for the temperature dependence of the heat capacity with account for these phase transitions. We calculate the temperature dependences of the thermodynamic functions: entropy, S0(T), enthalpy, H0(T) – H0(298.15), and the reduced thermodynamicpotential, Φxx(T), of the studied manganites.