Effect of monovalent doping on the physical properties of La_0.7Sr_0.3MnO₃compound synthesized using sol-gel technique

Abstract

In this work, we have studied the effect of monovalent substitution on the structural, magnetic and magnetocaloric properties of the P-doped La0.7Sr0.2M0.1MnO3 (M = Na, K) manganites synthesized by sol-gel technique. Structural investigations using X-ray diffraction show that all the elaborated compounds crystallize in the rhomboedral structure with R-3c space group. The increase in the ionic radius <rA> induces a rotation of MnO6 octahedra leading to a change in the Mn-O-Mn angles and the Mn-O distances. Magnetizations measurements were carried out using vibrating sample magnetometer operating above room temperature with magnetic applied field up to 5 tesla. All our samples exhibit paramagnetic to ferromagnetic transition with a Curie temperature above room temperature. From magnetic measurements versus magnetic applied field at several temperatures, we have determined the magnetocaloric effect using the classical thermodynamics based on Maxwell relations.