Study of the Physical Properties of the New Spinel Oxide NaMgMn2O4 Material

This study explores the properties of NaMgMn2O4 spinel oxide, focusing on its structural, magnetic, electronic, optical, and thermoelectric characteristics through density functional theory (DFT) calculations using the Wien2k package. The results reveal that NaMgMn2O4 is a semiconductor with spin-dependent band gaps, where the spin-up state has a band gap of 0.473 eV and the spin-down state exhibits a larger gap of 2.846 eV. This indicates that spin-up electrons require less energy for excitation from the valence to the conduction band, a typical behavior of semiconductors. The asymmetry between spin-up and spin-down states in the total density of states (TDOS) further supports the magnetic nature of the material. In terms of optical properties, the real part of the optical conductivity increases with energy, reaching a maximum peak, especially in the zz direction, before declining at higher energy levels. The imaginary part of the optical conductivity, which reflects energy loss due to photon absorption or emission, shows negative values at lower energies, transitioning to positive values as energy increases. Thermoelectric performance, assessed through the Seebeck coefficient (S), shows a peak at 300 K, suggesting that this is the optimal temperature for converting thermal to electrical energy. However, beyond 300 K, the Seebeck coefficient decreases, indicating reduced efficiency. This decline is likely due to the interplay between carrier concentration and mobility, where higher temperatures lead to increased carrier scattering and reduced mobility, thereby lowering the Seebeck coefficient.