Investigation of Structural, Magnetic and Magnetocaloric Properties of La0.67-xNdxCa0.18Sr0.15MnO3 (0.00≤x≤0.10) Manganites

In this thesis study, the synthesis and characterization of manganite-based materials with potential use in magnetic refrigeration systems were aimed. For this purpose, the effects of Nd substitution at different concentrations in place of La on the structural, magnetic, and magnetocaloric properties of La0.67-xNdxCa0.18Sr0.15MnO3 compounds were investigated. Structural analyses and morphological examinations were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). In order to determine the magnetic properties, temperature- and magnetic field-dependent magnetization measurements were performed using a Physical Property Measurement System (PPMS). According to the XRD results, it was determined that the structures possess a rhombohedral crystal structure and all samples belong to the R-3c space group. SEM images revealed that the average grain size increases gradually with increasing Nd doping concentration. From M(T) measurements, it was observed that when Nd was substituted for La at a level of x = 0.02, the Curie temperature (TC) increased to 313.94 K. However, at higher doping levels, the TC was found to decrease gradually with increasing Nd concentration. When the magnetic entropy change (ΔSM) values were examined, the maximum value was obtained as 6.41 Jkg⁻¹K⁻¹ under 5 T for the La0.57Nd0.10Ca0.18Sr0.15MnO3 sample with the highest Nd content. Furthermore, evaluation of the RCP values calculated from the ΔSM curves indicated that the RCP values increase with increasing Nd doping.