Enhanced THz Emission and Chirality Control in van der Waals Ferromagnetic FePd₂Te₂/Pt Heterostructures

Two-dimensional (2D) magnetic materials, with their unique van der Waals (vdW) layered structure, tunable magnetism, and strong spin-orbit coupling, are promising for spintronic applications like terahertz (THz) emitters. Our study investigates the THz radiation properties of the newly discovered vdW ferromagnet FePd₂Te₂, which features a one-dimensional Fe zigzag chain structure and strong in-plane uniaxial anisotropy. Using ultrafast reflective THz emission spectroscopy (TES), we demonstrate that the paramagnetic FePd₂Te₂ produces weak THz emission at room temperature. However, when capped with a 3 nm Pt layer, the THz emission intensity is significantly enhanced, attributed to spin-to-charge conversion (SCC) via the inverse spin Hall effect (ISHE). In the FePd₂Te₂/Pt heterostructure, the THz emission intensity is closely linked to the spin texture induced by crystal twinning in FePd₂Te₂ and depends on the polarization angle of the pump laser. Two mechanisms for the photoexcited spin current generation are identified: one from spin-polarized hot electrons at the FePd₂Te₂/Pt interface, and the other, which is dominant, from angular momentum transfer through a nonlinear optical effect that induces impulsive magnetization. These findings provide valuable insights into the spin dynamics of 2D materials and open avenues for high-density, low-power THz spintronic device development based on advanced 2D vdW magnets.