Analysis and control of terahertz radiation parameters in CoFeB/(Pt, W, Ta) structures

This work presents a study of a series of spintronic terahertz emitters based on bilayer structures consisting of layers of ferromagnetic Co$_{20}$Fe$_{60}$B$_{20}$ and heavy metals Pt, W, and Ta. The results confirm that the mechanism of terahertz generation in the investigated series is related to the inverse spin Hall effect. It is shown that the terahertz emitter with a non-magnetic Pt layer produces terahertz radiation with an amplitude an order of magnitude higher than that of structures based on W and Ta, which is due to the larger value of the spin Hall angle. The study also demonstrates the possibility of controlled manipulation of the polarization of terahertz radiation in the developed series by using an external magnetic field applied in the direction of the hard magnetization axis.