Multifunctional chiral glass nanocomposite via thermal poling: Induced circularly polarized luminescence, ferromagnetism, and nonlinear optics

This study reports a thermally poled Fe2TiO5/Bi2O3/B2O3 system exhibiting chiroptical, nonlinear optical, and ferromagnetic properties. Through thermal poling at 3 kV/mm and 390 °C, the glass nanocomposite undergoes an orthorhombic-to-monoclinic phase transition in Fe2TiO5, creating chiral-active units and oxygen vacancies (Ov). The optimized sample demonstrates exceptional circularly polarized luminescence with dissymmetry factor gₗᵤₘ = -0.88 and intense photoluminescence at 420 nm with a 35.12 ns lifetime, enabled by Rashba-effect-driven spin-selective transitions. Electron paramagnetic resonance spectroscopy reveals spin-canted Fe3+ in distorted FeO4 (g = 6.8, D = 1.8 cm−1) and FeO6 (g = 4.3, D = 0.5 cm−1) environments, while vibrating sample magnetometer measurement confirms room-temperature ferromagnetism (Ms = 3.10 emu/g, Hc = 0.28 T) through Dzyaloshinskii-Moriya interactions. The material simultaneously exhibits strong second-harmonic generation at 532 nm with a second-order susceptibility χ(2) of 11.4 pm/V (quadratic intensity dependence, slope = 1.97) and large nonlinear refraction (χ(3) = 9.84 × 10−11 esu), attributed to interfacial hyper-polarizability from aligned [TiO6]-[FeO4] dipoles. Density functional theory calculations support these findings with a predicted direct bandgap of 2.05 eV. This multifunctional nanocomposite opens new possibilities for integrated chiral photonic and spintronic devices.