Effect of K-doping on the structural, magnetic and magnetocaloric properties of Pr0.8Na0.2-xKxMnO3 (0 ≤ x ≤ 0.15) manganites

In this paper, the effect of potassium K substitution on morphological, crystallographic and magnetic properties of the Pr0.8Na0.2MnO3 perovskite was investigated. All samples were synthesized using the Pechini sol-gel method. On the one hand, the morphological study showed that the grains are irregularly spherically-shaped and have a submicronic size. On the other hand, the chemical analysis expectedly unveiled the presence of all the predicted elements in the right composition. Through the X-ray diffraction analysis, we proved that the prepared compounds crystallize in the orthorhombic structure with the Pbnm space group. The temperature dependence of the magnetization M (T) showed a large increase of M when x increases from 0 to 0.05, as does the Curie temperature TC. The transition from ferromagnetic (FM) to charge ordered antiferromagnetic (CO-AFM) phase at high temperature is observed for x = 0, however the doped manganites exhibit only an FM metallic phase. The magnetocaloric effect (MCE) was calculated according to the Maxwell relation based on magnetic measurements. The magnetic entropy change (DSM) reaches a maximum value which remains constant when increasing the K content. The highest value of the relative cooling power RCP was found to be 277 J/kg for the Pr0.8Na0.05K0.15MnO3 under an applied magnetic field of 5 T. (C) 2016 Elsevier B.V. All rights reserved.