Structural, magnetic, magnetocaloric effect and critical behavior of La0.7Sr0.3−x□xMnO3(0 ≤ x ≤ 0.05)

From magnetization measurements as function of temperature and magnetic applied field, we have noticed a large magnetic entropy change (∆SM) around Curie temperature. ∆SM is found to decrease with the deficiency content (2.30 J/kg·K for x = 0-1.33 J/kg·K for x = 0.05 under magnetic field change µ0∆H = 5 T). This behavior is accompanied by a slight reduction of the Curie temperature (TC = 338 and 328 K for x = 0 and 0.05, respectively). These results show that our materials are potential candidates for magnetic refrigerants working in above room temperature. The refined values of the critical exponents β, γ and δ obtained from the modified Arrott plots and Kouvel-Fisher method indicated that the behavior of the parent sample and the samples with 1and 3% of strontium-deficient are characterized by long-range mean-field behavior (with β = 0.50; γ = 1). However, for 5% lacuna, the magnetic behavior is close to the theoretical 3D-Heisemberg prediction with short-range exchange coupling.