High-efficiency Pt75Au25-based spintronic terahertz emitters

Spintronic terahertz emitters (STEs) generate broadband THz radiation via ultrafast spin–charge conversion in magnetic multilayers, offering spectral coverage beyond that of photoconductive antennas and nonlinear optical crystals. Here, we demonstrate STEs based on a PtxAu100−x alloy that achieve significantly higher THz output power than widely used Pt-based devices. Alloy composition and layer thickness tuning yield Pt75Au25 as the optimal alloy, providing a 30% increase in THz power in CoFeB/Pt75Au25 bilayer STEs compared to the optimized CoFeB/Pt reference STE. In W/CoFeB/Pt75Au25 trilayer STEs, we observe a 10% higher THz power than in the optimized W/CoFeB/Pt trilayer. The STE efficiency is reduced upon annealing for both Pt75Au25- and Pt-based STEs due to the formation of interfacial alloys. Our results establish Pt75Au25 as a promising platform for high-performance STEs, where its giant spin Hall effect significantly enhances efficiency over conventional Pt-based devices.