Magnetocaloric properties in the Pr0.7Sr0.3-xCaxMnO3: Direct and indirect estimations from thermal diffusivity data

Magnetization, specific heat, thermal diffusivity, and magnetocaloric effect were studied in Pr_0.7Sr_0.3-xCa_xMnO₃ system (x = 0; 0.1; 0.2; 0.3) in the temperature range of 80–320 K and in a magnetic field of 18 kOe. A correlation was found between the coefficients under study and microscopic characteristics 〈r_A〉 – average ionic radius and σ² – cationic disorder). The decrease in σ² and 〈r_A〉, caused by the substitution of Sr atoms by Ca atoms, causes a weakening of the exchange interactions and a decrease in T_C. The observed minima in the temperature dependence of thermal diffusivity η(T) near T_C are associated with the appearance of an additional channel of phonon relaxation in fluctuations of the magnetic order parameter. A relationship was found between the MCE value and the change in thermal diffusivity in a magnetic field near T_C. This relationship can be applied as another MCE evaluating indirect method. It is shown that MCE value estimation from thermal diffusivity data is consistent with the results of caloric measurements.