Research overview
Spintronic terahertz emitters generate broadband THz pulses when a femtosecond laser drives spin currents from a ferromagnetic layer into a heavy metal. Their polarization follows the magnetization, so rotating it has usually needed rotating magnets, multipolar bias fields or cascaded emitters. This paper replaces the ferromagnetic layer with an anisotropic FeCo/TbCo₂/FeCo trilayer that has a uniaxial easy axis. Sweeping a magnetic field applied along the hard axis then rotates the THz polarization smoothly through a full 360°, following near-Stoner–Wohlfarth magnetization behaviour. The emission efficiency is only marginally lower than a standard Pt/CoFeB/W inverse-spin-Hall emitter. A model of imperfect Stoner–Wohlfarth switching agrees with the measurements. The authors show the emitter’s use for polarimetry, without mechanically rotating optics, by characterising the birefringence of a quartz plate.
Key findings
- Full 360° rotation of THz polarization from a spintronic emitter using a single bias field
- Uniaxial FeCo/TbCo₂/FeCo trilayer follows near-Stoner–Wohlfarth magnetization behaviour
- Emission efficiency only marginally below a standard Pt/CoFeB/W emitter
- THz polarimetry without rotating optics, demonstrated on quartz birefringence
