Figure 7.

Roadmap to efficient spintronic THz-emitters with high signal strength and broad bandwidth. Here, ${\mathrm{\Theta }}_{\mathrm{SH}}$ is the spin-Hall-angle, λ_SD is the spin-diffusion-length, T and ${\tau }_{\mathrm{el}}$ are the interface transmission parameter and the elastic scattering lifetime, respectively. t_FM, t_NM, σ_FM and σ_FM are the FM and NM layer thickness and electrical conductance, respectively. n_i and ${\kappa }_{\mathrm{i}}$ are the index of refraction and the absorption coefficient of all involved layers (metalls and insulators) in the THz-range, respectively. M_tot is the transfer matrix for the total layer stack.