Critical behavior and magnetocaloric effect of Pr1-xCaxMnO3

The critical behavior of Pr1-xCaxMnO3 samples with x = 0.25, 0.27, and 0.29 has been investigated. Detailed analyses of magnetic-field dependences of magnetization at temperatures around the paramagnetic-ferromagnetic transition, M(H, T), reveal that the samples undergo a second-order magnetic phase transition. The Arrott plot method predicts the values of critical parameters to be T-C approximate to 118 K, beta = 0.351 +/- 0.003, gamma = 1.372 +/- 0.002, and delta = 4.90 +/- 0.02 for x = 0.25; T-C approximate to 116 K, beta = 0.362 +/- 0.002, gamma = 1.132 +/- 0.004, and delta = 4.09 +/- 0.03 for x = 0.27; and T-C approximate to 110 K, beta= 0.521 +/- 0.002, gamma = 0.912 +/- 0.005, and delta = 2.71 +/- 0.02 for x = 0.29. The values of beta = 0.351 (for x = 0.25) and beta = 0.362 (for x = 0.27) are close to the value beta = 0.365 expected for the 3D Heisenberg model, proving an existence of short-range ferromagnetic interactions in these samples. A slight increase in Ca-doping content (x = 0.29) leads to the shift of the beta value (-0.521) towards that of the mean-field theory (with beta = 0.5) characteristic of long-range ferromagnetic interactions. The samples also exhibit a magnetocaloric effect: around T-C of Pr1-xCaxMnO3 compounds, magnetic-entropy change reaches the maximum values of about 5.0, 4.1, and 2.5 J kg(-1) K-1 for x = 0.25, 0.27, and 0.29, respectively, under an applied-field change of 50 kOe. Magnetic-field dependences of the maximum magnetic-entropy change (Delta S-max) obey a power law vertical bar Delta S-max(H)vertical bar proportional to H-n, where exponent values n = 0.68-0.74 are close to those obtained from the theoretical relation n = 1 + (beta - 1)/(beta + gamma). (c) 2015 AIP Publishing LLC.