Özet:
In this work, the structural and magnetic properties of the polycrystalline La0.85Ag0.15MnO3 (LAM) and (La0.80Pr0.20)(0.85)Ag0.15MnO3(LPAM) compounds prepared by the sol-gel method were investigated. The structural properties of both polycrystalline compounds were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectrum (EDX) methods. The XRD results showed that both samples crystallized in the hexagonal symmetry with space group. The SEM images showed that the particles are closely packed with each other, and their size range from 0.5 to 2.0 mu m with the average sizes of 1.23 and 1.03 mu m, for LAM and LPAM, respectively. From the EDX spectrum, in both compounds, we did not see loss of any integrated elements during the sintering process and no other impurity elements. The magnetic properties were studied by employing temperature M(T) and external magnetic field M(H) dependence of magnetization measurements. Both compounds showed magnetic phase transition from paramagnetic to ferromagnetic phase. With the substitution of Pr for La, the Curie temperature, T (C), decreased from 262 to 216 K. At a field change of 5 T, LAM and LPAM showed large magnetic entropy changes of 7.90 and 4.96 J kg(-1) K-1, respectively. Furthermore, their relative cooling power (RCP) values were found as 213.32 and 263.02 J kg(-1), respectively. These findings make both LAM and LPAM compounds as good candidates for the practical magnetic refrigeration.
