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.