Study of Optical, Magnetic, and Magnetocaloric Properties of Double Perovskites Dy₂NiMnO₆: First Principles Approach and Monte Carlo Simulations

The magnetocaloric and optical properties of Dy₂MnNiO₆ (DMNO) were investigated using first-principles calculations and Monte Carlo simulations. The calculated magnetic exchange interactions reveal ferromagnetic couplings between the magnetic ions. The Mn-Ni interactions in DMNO are found to be long-range ferromagnetic, indicating the localization of 3d-orbitals in the presence of 4f orbitals. The analysis of the density of states, suggesting a strong ferromagnetic superexchange interaction between Mn and Ni, which is mediated by the oxygen ions. DMNO exhibits a maximum entropy change and relative cooling power are found. DMNO displays a strong frequency dependence, characterized by a high static refractive index. The real dielectric function is notably high, reflecting the refractive index measured at low frequencies. The absorption coefficient in the visible and near-infrared regions is relatively low. Conversely, its high reflectivity in these regions suggests a reflective property.