شريفه عبدالله مجيليب الحلافي2022-05-182022-05-187382https://drepo.sdl.edu.sa/handle/20.500.14154/414The purpose of this work is to present the findings of an experimental analysis of structural, magnetic, and magnetocaloric properties of the nanocrystalline manganites, La0.8Sr0.15Na0.05MnO3 (LSNMO), with size about 50 nm elaborated via solgel route. X-ray diffraction presents that LSNMO crystallize in a rhombohedral structure with the 3Rc space group. Magnetic characterizations demonstrate that LSMNO exhibits a coexistence of interacting superparamagnetic (ISPM) phase with blocking temperature TB = 194 K and a ferromagnetic phase with Curie temperature TC = 255.5 K. At low temperatures, the SPM state undergoes a collective freezing state at Tf = 46 K. The maximum magnetic entropy change ( M pk S ) is about 1.41 Jkg-1K-1 and the refrigeration capacity (RC) is 288 JKg-1 for a field change of 5 T at T = 215 K. The magnetocaloric response is reasonably high compared to the bulk materials, and this makes nanoparticles of LSMNO a potential candidate material for active magnetic refrigerators.ar-SAThesis