Demonstrates tunable terahertz emission in multiferroic systems, suggesting a novel approach for spintronic devices.
The spintronic THz emitter, driven by an ultrafast spin current induced by laser pulse irradiation in nanoscale nonmagnetic heavy metal (NM)/ferromagnetic metal (FM) bilayer films, is attracting attention owing to its broad bandwidth, simple device structures, abundant material candidates, and high controllability. In this study, we demonstrate that spin-current-driven THz emission is tunable depending on the direction of in-plane spontaneous electric polarization without applying an external electric field in an artificial multiferroic system consisting of NM/FM/ferroelectric (FE) junctions. Time-domain THz spectroscopy indicates that THz signal amplitude in a Pt/Ni 81 Fe 19 /X-cut LiNbO 3 structure varies by over 15%, where THz signals are enhanced when the in-plane electric polarization direction is perpendicular to the magnetization of FM. These polarization-direction-dependent THz emission behaviors may originate from the modulation of spin transport properties through photostriction in LiNbO 3, which develops an unconventional pathway to tune spin-current-driven THz emission, providing a basis for bias-free tunable spintronic THz emitters.
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Mori et al. (2026) studied this question.
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