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 Pr0.7Sr0.3-xCaxMnO3 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 ( - average ionic radius and sigma(2) - cationic disorder). The decrease in sigma(2) and 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 eta(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. (C) 2018 Elsevier B.V. All rights reserved.