Critical Behavior and Magnetocaloric Effect of Pr1-xSrxCoO3

The modified Arrott plot method was used to analyze magnetic-field dependences of magnetization, M(H), for two polycrystalline samples Pr_1-xSr_xCoO₃ with x = 0.4 and 0.5. The analyses determined the values of critical parameters T_C ≈ 204 K, β = 0.654 ± 0.016, y = 1.11 ± 0.009, and δ = 2.70 ± 0.009 for x = 0.4, and T_C ≈ 218 K, β = 0.495 ± 0.004, y = 0.991 ± 0.003, and δ = 2.86 ± 0.009 for x = 0.5. With these critical values, the M(H) data around the T_C of the samples fall into two universal branches of a scaling function M(H, ε) = |ε|^βf_±(H/|ε|^β+y), where ε = (T-T_C)/T_C, and f₊ for T > T_C and f_ for T <; T_C. Here, the T_C increase with the increasing Sr content is ascribed to an increase of ferromagnetic (FM) double-exchange interaction pairs of Co³⁺-Co⁴⁺, and to the β change from 0.654 (for x = 0.4) to 0.495 (for x = 0.5). This corresponds to the change in FM interactions from short-range to nearly long-range FM orders. Based on the M(H) data, we also determined the magnetic-entropy change, which reaches a maximum value (|ΔS_max|) around the T_C; |ΔS_max| ≈ 1.9 and 2.2 J/kg · K for x = 0.4 and 0.5, respectively, for a magnetic field change ΔH = 50 kOe. The relative cooling power thus increases from 52 J/kg (for x = 0.4) to 84 J/kg (for x = 0.5). In particular, field dependences of the magnetic-entropy change (ΔS_m) obey a power function |ΔS_m (H)| ∝ Hⁿ, where the magnetic-ordering parameter (n) slightly decreases from 0.75 for x = 0.4 to 0.70 for x = 0.5.