High-efficiency Pt$_{75}$Au$_{25}$-based spintronic terahertz emitters

Abstract

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 a new type of STE based on PtxAu100-x alloy that achieves 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/Pt$_{75}$Au$_{25}$ 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 Pt$_{75}$Au$_{25}$- and Pt-based STEs due to formation of interfacial alloys. Our results establish Pt$_{75}$Au$_{25}$ as a promising platform for high-performance STEs, where its giant spin Hall effect significantly enhances efficiency over conventional Pt-based devices.