Large Magnetocaloric Effect Around Room Temperature in Double-Exchange Ferromagnets Pr1-xSrxMnO3 With Short-Range Interactions

We present a detailed study on a large magnetocaloric effect at room temperature in polycrystalline ceramic samples of Pr1-xSrxMnO3 (x = 0.3, 0.4, and 0.45), exhibiting a second-order phase transition. The experimental results demonstrate the replacement of Sr2+ for Pr3+ in Pr1-xSrxMnO3, which leads to the Curie temperature (T-C) increasing from 258 K for x = 0.3 to 301 K for x = 0.45. In particular, the maximum values of magnetic entropy change (|Delta S-max|) in the field H = 10 kOe are about 2.36-3.33 J.kg(-1).K-1, corresponding to the refrigerant capacity RC = 50 -53 J.kg(-1) for x = 0.3-0.45. Based on the modified Arrott-plot method and the isothermal magnetization data around T-C, we obtained the values of the critical exponents (beta, gamma, and delta) and T-C for all the samples. Here, the values beta = 0.370-0.397 are quite close to those expected for the 3-D Heisenberg model. This proves that ferromagnetic short-range interactions are present in Pr1-xSrxMnO3 compounds. In addition, magnetic-field dependences of |Delta S-max| obey the power law, |Delta S-max| similar to H-n, where the field exponent n approximate to 0.6 is close to the value calculated from the relation n = 1 + (beta - 1)/(beta + gamma).