Terahertz Optical Properties of Zn 0.5 Fe 2.5 O ₄ Nanoparticles

Sol–gel synthesized Zn 0.5 Fe 2.5 O 4 nanoparticles (ZNF NPs) were investigated for their terahertz (THz) optical properties using terahertz time‐domain spectroscopy (THz‐TDS). ZNF NPs with an average crystallite size of ≈8 nm exhibited superparamagnetic behavior at room temperature (300 K), with a blocking temperature near 154 K. THz‐TDS measurements revealed a consistent reduction in transmittance with increasing sample thickness. THz‐optical analysis yielded a stable refractive index of ≈2.52 and a low extinction coefficient of ≈0.08. The corresponding real and imaginary parts of the dielectric constant ( ε ′ and ε ″) were found to be 6.34 and 0.3–0.6, respectively. A low loss tangent from 0.05–0.095 highlights the potential of ZNF NPs for integration into THz‐frequency electronic devices.