Impact of oxygenated annealing on the magnetic and magnetocaloric properties of La_0.7Ca_0.3MnO₃ compound

La_0.7Ca_0.3MnO₃ (LCMO) is a prominent semi-metallic ferromagnet known for its strong spin polarization and sharp magnetic transition temperature. This makes it a highly attractive candidate for various applications in spintronic technology, memory devices, and multifunctional systems. The structural and physical properties of LCMO can be significantly altered by adjusting the annealing atmosphere during synthesis. Here, we present an in-depth analysis on the influence of oxygen annealing on the structural characteristics, magnetic behavior, and magnetocaloric properties of LCMO compound. The analysis of X-ray diffraction patterns by using Rietveld refinement method revealed that all the samples formed an orthorhombic structure with the Pnma space group with a decrease in cell volume for samples (S2 and S3) annealed in oxygen atmosphere. The samples S1, S2, and S3 undergo ferromagnetic-paramagnetic phase transitions at 247, 263, and 264 K, respectively. This suggests that the oxygenated annealing induce the oxygen homogeneity in the sample. On the other hand, the field-dependent magnetization measurements and Arrott analysis indicated a first-order ferromagnetic phase transition in all the prepared samples. The maximum change in magnetic entropy was evaluated by using numerical approximation of Maxwells thermodynamic relation. It was noted that the maximum change in magnetic entropy shows monotonic behaviour with oxygen annealing. This ability to adjust magnetization and magnetocaloric effect by altering the annealing atmosphere of LCMO presents a novel approach for developing magnetic refrigerants and gaining insight into fundamental phenomena.