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

Abstract

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 (〈rA〉 – average ionic radius and σ2 – cationic disorder). The decrease in σ2 and 〈rA〉, caused by the substitution of Sr atoms by Ca atoms, causes a weakening of the exchange interactions and a decrease in ТС. The observed minima in the temperature dependence of thermal diffusivity η(T) near ТС 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 ТС. 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.