Spin-structured multilayer THz emitters by oblique incidence deposition

State-of-the-art THz spintronic emitters require a constant magnetic field to saturate their magnetization. We demonstrate that depositing the ferromagnetic layers at oblique incidence confines the magnetization to a chosen in-plane easy axis and maintains the saturation in the absence of an external magnetic field. We use this method to build THz emitters structured as spin valves, for which we use an external magnetic field to turn on and off the emission of THz radiation as well as to change its polarization. We are able to reproduce the THz waveforms by modeling the spin current and the THz propagation through the multilayer system.