This study investigates the impact of annealing temperature on the structural and magnetic attributes of Nd-substituted strontium hexaferrite (Sr0.9Nd0.1Fe12O19). The research demonstrated that as the annealing temperature increased, diffusion accelerated, thereby inducing a transformation into the SrFe12O19 phase and enhancing hard magnetic properties. The annealing process also significantly impacted the bonding structure, specifically affecting the presence of N-O bonds. Peak intensities escalated until 1100°C, subsequently declining due to the emergence of a composite structure (SrFe12O19+α-Fe2O3) arising from the Nd substitution. Importantly, the coercive field of the compound substantially increased post-annealing, attaining a peak at 1100°C (5.21 kOe) from 0.52 kOe pre-annealing, indicating that annealing amplifies resistance to demagnetization. Furthermore, both remanent magnetization and saturation magnetization values improved, reaching maximum values at 1100°C, measuring 40.2 emu/g and 61.5 emu/g, respectively.