An experimental investigation of vibrational, optical, and dielectric properties of Li–Mg ferrite for potential high-frequency and optoelectronic applications

Spinel lithium ferrites hold considerable significance in technological applications. Numerous investigations are conducted to explore the mechanisms underlying their properties. This work aims to detail the vibrational, optical, dielectric, thermodynamic, and magnetic properties of the LiMg_0.5Fe₂O₄ compound. Infrared and Raman spectroscopy further indicate the formation of the spinel phase in the samples. The optical study reveals a direct band gap with semiconducting characteristics, approximately 2.15 eV, with a low Urbach energy, indicating minimal disorder. Furthermore, precise calculations of thermodynamic parameters, including entropy change (ΔS), enthalpy change (ΔH), and free energy of activation (ΔF), provide additional insights into the properties of the compound. High dielectric permittivity values, reaching around 10⁵, are observed and attributed to the Maxwell–Wagner interfacial polarization mechanism. The remanent magnetization (M_r = 0.97 emu g⁻¹) and coercive field (H_C = 4.55 Oe) extracted from the M–H loop are both notably low, clearly indicating the superparamagnetic nature of the sample. Our results show that LiMg_0.5Fe₂O₄ ferrite is a promising candidate for applications in multifunctional devices.