Sol–gel synthesis was used to prepare M-type strontium hexaferrite (SrFe12O19) nanoparticles, which were thoroughly analyzed through both first-principles calculations and experimental characterization techniques. The phase formation and structural development were investigated using X-ray powder diffraction along with Rietveld refinement, confirming the formation of a highly crystalline single-phase hexagonal magnetoplumbite structure with space group P63/mmc. No impurity phases were detected, while systematic peak broadening was observed without any noticeable peak shifting. The lattice parameters a and c were found to of 5.776 Å and 22.054Å, respectively. Dielectric constant and AC electrical resistivity exhibited enhanced values, and dielectric measurements revealed relaxation behavior at higher frequencies. Density functional theory calculations within the GGA- PBE framework indicate a semiconducting nature with an indirect band gap of approximately 1.81 eV, dominated by Fe-3d and O-2p electronic states. Optical analysis demonstrates strong ultraviolet absorption, low reflectance in the visible region, and a pronounced dielectric response, while elastic property evaluation confirms direction-dependent mechanical behavior due to elastic anisotropy. These results suggest that SrFe12O19 nanoparticles are promising candidates for advanced magnetic devices, optoelectronic applications, and microwave miniaturization technologies.