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 Pr_1-xSr_xMnO₃ (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 Pr_1-xSr_xMnO₃, which leads to the Curie temperature (TC) increasing from 258 K for x = 0.3 to 301 K for x = 0.45. In particular, the maximum values of magnetic entropy change (|ΔS_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 TC, we obtained the values of the critical exponents (β, γ, and δ) and TC for all the samples. Here, the values β = 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 Pr_1-xSr_xMnO₃ compounds. In addition, magnetic-field dependences of |ΔS_max| obey the power law, |ΔS_max| ~ Hn, where the field exponent n ≈ 0.6 is close to the value calculated from the relation n = 1 + (β - 1)/(β + γ).