Observation of tunable terahertz optical response in nanoscale lithium ferrite driven by magnetic field and laser

With the advancement of spintronics, tunability has emerged as a highly sought-after attribute of magnetic materials. Nevertheless, the comprehension of the terahertz (THz) optical characteristics of tunable magnetic materials driven by external excitation fields remains limited, necessitating further qualitative and quantitative investigation. Here we demonstrate the tunable optical properties of the LiFe 5 O 8 (LFO)/F-Mica structure under magnetic field by a THz time-domain spectroscopy (THz-TDS) system. The prepared LFO/F-Mica structure shows significant changes in dielectric properties and absorption coefficients under different magnetic fields, which is attributed to the interaction of the magnetic field with the spins of ordered magnetic ions (Fe 3+ ) located in a non-centrosymmetric coordination environment. In addition, we investigate the specific contribution of the external laser field to the THz optical parameters of the LFO/F-Mica. The dielectric properties and THz optical response of LFO/F-Mica significantly depend on the laser power under 532 nm laser pumping. The modulation effects of these diverse external fields reveal the potential of lithium ferrites for applications in the THz band. These findings offer valuable insights for the development of tunable multifunctional THz magnetic devices, with potential applications in the fields of communications, medicine, and nondestructive testing. • Synthesis of nanoscale lithium ferrite extends its operational bandwidth from microwave to terahertz regimes. • Tunable dielectric properties and absorption coefficients achieved by multiple physical fields (magnetic and laser). • Application of soft mode theory and spin-orbit coupling to probe the tunable terahertz response of lithium ferrite. • Prepared LiFe 5 O 8 /F-Mica can be applied to terahertz magnetic modulators with high degree of freedom.