Effect of A-site deficiency on the structural and magnetic properties of La0.8−x□xNa0.2−x□xMnO3 oxides and estimation of the magnetocaloric behavior

Abstract

The morphological, structural, magnetic and magnetocaloric properties of perovskite manganite oxides La0.8−x□xNa0.2−x□xMnO3 are studied with x = 0 and 0.1. The X-ray diffraction (XRD) data were analyzed by Rietveld refinement technique which reveals that the samples crystallized in a rhombohedral structure with R3¯c space group. As for the magnetic measurements, it is found that the two samples undergo a transition from the ferromagnetic state (FM) to paramagnetic state (PM) with the increase of temperature. The transition temperature, called the Curie temperature (TC), decreases from 324 K for the parent compound (x = 0) to the range of room temperature (304 K) for x = 0.1. Moreover, from magnetization measurements versus magnetic applied field, we studied the magnetocaloric effect (MCE) by the determination of the magnetic entropy change ΔSM. The maximum magnetic entropy changes ΔSMMax increases from 2.91 J/kg.K for x = 0–3.23 J/kg.K for x = 0.1 under an applied magnetic field of 2 T. The Relative Cooling Power (RCP) values were found to reach 76.13 J/K and 70.36 J/K for x = 0 and 0.1, respectively, for the same applied magnetic field (μ0H = 2 T). Thanks to the mentioned values obtained around the Curie temperatures, these materials are suggested to be good candidates as magnetic refrigerants for magnetic refrigeration in the above-room and room temperature range. Besides, a mixture of these two materials may form a composite refrigerant working in a larger temperature range limited by their TC.