Reconfigurable chiral spintronic THz emitters

Abstract

Collective spin arrangements manifest diverse spin textures, encompassing ferromagnetism, antiferromagnetism, and chiral vortices. However, mapping these spin textures in ultrathin magnetic multilayers has remained elusive. We introduce a reconfigurable chiral spintronic terahertz emission method through investigations on a model system of synthetic antiferromagnet and extract the spin information of the individual ferromagnet (FM) layers. Upon femtosecond photoexcitation of the synthetic antiferromagnet (FM1/Ru/FM2), the ferromagnets generate a pair of linearly polarized ultrafast spin currents, which, after relaxation at the FM/Ru interface, emit corresponding THz pulses. The Ruderman–Kittel–Kasuya–Yosida interactions between the two FMs create magnetic-field-controlled spin textures, and the induced relaxation asymmetry at the interfaces leads to a phase shift in THz orthogonal fields, causing the radiation to change from linear to circular polarization. The method will provide an innovative probe for electronic and magnetic states in ultrathin spintronic heterostructures, low-dimensional quantum materials, topological insulators, Weyl semimetals and facilitate exploration of spin textures such as skyrmions, merons, and solitons.