Magnetocaloric effect and critical behavior in La0.8-xPrxSr0.2MnO3 (x=0.2, 0.4, 0.5) manganites

This paper reports on an investigation carried out to determine the effects of Pr substitution on the magnetocaloric and critical behavior of La0.8-xPrxSr0.2MnO3 (x = 0.2, 0.4, 0.5) manganites. Structural studies show that all the compositions are single phase with a rhombohedral structure. Moreover, the lattice parameters and unit cell volume decrease with increasing Pr concentration while the Curie temperature (T-c) decreases with Pr3+ substitution for La3+ ions. Arrot's plots are used to determine the nature of the second order magnetic transition; no obvious hysteresis loss is observed in the vicinity of Tc in any of the samples. An exhaustive study of the critical behavior of the paramagnetic to ferromagnetic transition is conducted to determine the values of the critical exponents (beta, gamma, and delta) based on the modified Arrot's plot and using the Kouvel-Fisher method. We have obtained the critical exponents used 3D-Heisenberg and 3D-Ising models. It was found that with increasing Pr doping the values of beta and gamma decrease and increase, respectively. This suggests an increase in the ferromagnetic short-range order as a result of increasing Pr content in the La(0.8-)x PrxSr0.2MnO3 samples. Maximum changes in the magnetic entropy were found to be 4.16, 3.88, and 3.8 J kg(-1) K-1 under an applied magnetic field of 5 T while the Relative Cooling Power (RCP) values reached 174.7, 252.3, and 255 J kg(-1) for x = 0.2, 0.4, and 0.5, respectively.