Tailoring spintronic terahertz emitters for special applications

Abstract

Ultrafast spintronics is a key frontier for next-generation technologies enabling operating speeds beyond those of conventional electronics. This thesis presents a rigorous investigation of spintronic effects induced by femtosecond laser excitation in diverse magnetic multilayers, with a focus on the conceptualization and development of terahertz (THz) spintronic devices using state-of-the-art Spintronic Terahertz Emitters (STEs). In particular, this work examines the importance of charge dynamics in shaping the ultrafast response. Extending this analysis to miniaturized systems, the influence of charge dynamics in periodically patterned STEs is addressed, notably causing systematic modifications in the emission spectrum as emitter size decreases. Experiments using a free-space pump-probe setup, supported by a comprehensive analytical model, validate and quantitatively reproduce these effects, providing a predictive tool for tailoring spectra through nanopatterning. Building on these insights, the work presents applications including narrowband THz emitters, ultrafast digital-to-analog conversion with on-chip detection, electrically controlled magnetization switching, transient magnetoresistance studies, thermoelectric effects, and a switchable THz emitter device. Together, these findings advance the understanding of ultrafast spintronic technology and lay the groundwork for transformative advancements in ultrafast signal processing and the deployment of versatile spintronic THz devices.