**Abstract**

Diluted magnetic semiconductor (DMS) materials have gained a lot of attention in the last decade due to their possible use in spintronics. In this chapter, the effect of transition metal (TM) i.e., Mn and Fe doping on the structural, electronic, magnetic as well as optical properties of pure and doped LuN has been presented from the first principles density functional theory (DFT) calculation with the Perdew-Burke-Ernzerhof-generalized gradient approximation (PBE-GGA) and Tran Blaha modified Becke-Johnson potential (TB-mBJ) as correlation potentials. The predicted Curie temperature is expected to be greater than room temperature in order to better understand the ferromagnetic phase stability, which has also been confirmed through the formation and cohesive energies. The calculated lattice constants for perfect LuN (rock-salt structure) are in good agreement with the experimental values. Interestingly, doping of Mn and Fe on pure LuN displays indirect band gap to a direct band gap with half metallic and metallic character. The detailed analyses combined with density of state calculations support the assignment that the Half-magnetism and magnetism are closely related to the impurity band at the origin of the hybridization of transition states in the Mn-doped LuN. Absorption spectra are blue shifted upon increase in dopant contents and absorption peaks are more pronounced in UV region. The refractive index and dielectric constant show increase in comparison to the pure LuN. According to the Penn's model, the predicted band gaps and static actual dielectric constants vary. These band gaps are in the near visible and ultraviolet ranges, as well as the Lu0.75TM0.25N (TM = Fe, Mn) materials could be considered possible candidates for the production of optoelectronic, photonic, and spintronic devices in the future.

**Keywords:** density functional theory, spintronics, LuN, doped nitrides, electronic structure, magnetism, optical properties
