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

Abstract

In this paper, we present the effect of Strontium vacancies on the structure and magnetic properties of La0.7Sr0.3−x□xMnO3 nano-sized compounds (x=0; 0.01; 0.03 and 0.05), synthesized using the sol-gel method. X-ray diffraction revealed that these manganites crystallized in the rhombohedral structure with space group R3-C.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 (2.30J/kg·K for x=0–1.33J/kg·K for x=0.05 under magnetic field change µ0∆H=5T). This behavior is accompanied by a slight reduction of the Curie temperature (TC=338 and 328K 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.