Giant magnetothermal anomalies and direct measurements of the magnetocaloric effect in Pr0.7Sr0.3−xBaxMnO3 manganites.

The paper presents the results of a study of magnetization, specific heat (C P), thermal diffusivity (η), thermal conductivity (κ) and direct measurements magnetocaloric effect of polycrystalline samples Pr 0.7 Sr 0.3−x Ba x MnO 3 (x = 0–0.3). An increase in the Ba concentration leads to a decrease in the Curie temperature (T C), an increase in the disorder parameter (σ 2) and a noticeable increase in thermal conductivity of the ferromagnetic phase (FM). The κ(Т) data near Т С revealed small minima and a sharp jump-like change in thermal conductivity upon transition to the FM phase. These results suggest that the anomalies in the temperature dependences of η(Т) and κ(Т) are associated with the scattering of thermal phonons both from distortions of the crystal lattice and from spin fluctuations. The giant change of η (Δη/η ∼ 67%) and κ (Δκ/κ ∼ 33%) was found in a magnetic field of 1.8 T for the x = 0 (Pr 0.7 Sr 0.3 MnO 3) sample. The maximum values of ∆T, ∆S and relative cooling power (RCP), observed for this sample in a field of 1.8 T, are equal to 1.81 K, 3.38 J/kg K and 74.02 J/kg, respectively. In the studied Pr 0.7 Sr 0.3−x Ba x MnO 3 samples, the specific cooling power value at f = 0.2 Hz is 0.35, 0.29, 0.21, and 0.11 W/g for x = 0, 0.1, 0.2, and 0.3 sample, respectively. • Specific heat, thermal diffusivity, and thermal conductivity of polycrystalline samples Pr 0.7 Sr 0.3-x Ba x MnO 3. • An increase in Ba concentration leads to a decrease in T C , an increase in disorder parameter. • Magneto-thermal diffusivity (Δη/η) and magneto-thermal conductivity (Δκ/κ) in a 1.8 T magnetic field for Pr 0.7 Sr 0.3-x Ba x MnO 3 was study. • Gigantic values of changes Δη/η ∼ 67% and Δκ/κ ∼ 33% were found in a magnetic field of 1.8 T for a sample with x = 0. • Direct measurements of adiabatic temperature change in a cyclic magnetic field 1.8 T. [ABSTRACT FROM AUTHOR]