Structural, Magnetic, and Magnetocaloric Effects of La_0.8Sr_0.2MnO₃ Manganites by Doping with f-Orbital Ions Through First-Principles Calculations

In this study, La_0.63Sr_0.2Nd_0.17MnO₃ was synthesized by the sol-gel method, and its structural, morphological, magnetic, and magnetocaloric effects were investigated. The structural properties were analyzed by x-ray diffraction (XRD), and scanning electron microscopy (SEM) was used to characterize the morphology. An integrated magnetic measurement system was used to determine the magnetic properties. La_0.63Sr_0.2Nd_0.17MnO₃ crystallized in a hexagonal crystal system with space group R-3c. This was also confirmed by Rietveld refinement of the x-ray data from La_0.63Sr_0.2Nd_0.17MnO₃. With the doping of Nd³⁺, the cell volume decreases, which can be explained by the angles and bond lengths of the bonds between the Mn and O ions and the distortion of the lattice. Near the Curie temperature, La_0.63Sr_0.2Nd_0.17MnO₃ exhibits significant magnetocaloric effects. The magnetic study of La_0.63Sr_0.2Nd_0.17MnO₃ suggests that the transition from the paramagnetic to ferromagnetic phase can occur near the Curie temperature. The maximum magnetic entropy change and relative cooling power (RCP) of La_0.63Sr_0.2Nd_0.17MnO₃ (298 K, 3 T) are 2.70 J/(kg K) and 135 (J/kg), respectively. The effect of f-orbitals on the magnetic properties of La_0.8Sr_0.2MnO₃ was investigated by first-principles calculations in density functional theory. Thus, it can be concluded that the magnetocaloric effects of the material after doping with f-orbital ions (Nd³⁺) is enhanced compared to La_0.8Sr_0.2MnO₃.