Magnetic alloy spintronic THz emitters

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Electromagnetic radiation in the frequency range from 0.3 to 30 THz is highly useful for spectroscopy and imaging in fundamental scientific research, as well as for applications such as quality control, security technologies and telecommunications. Ultrafast spintronic emitters represent a new type of THz sources. Commonly, they are ferromagnetic/non-magnetic systems such as Fe/Pt, relying on the inverse spin Hall effect. Pumping this structure with a femtosecond laser pulse launches a spin current from the magnetic into the non-magnetic layer. There, the inverse spin Hall effect subsequently converts the spin current into an ultrafast charge current, which acts as a source of broadband THz radiation. Recently, first experimental results on magnetic alloy systems lacking a single interface layer have demonstrated the need for a comprehensive understanding of the THz generation mechanism(s). The goal of this joint project is to systematically investigate magnetic alloy spintronic THz emitters and to gain an understanding of the underlying THz generation process(es). We will prepare different magnetic alloys of various compositions and measure the impact of non-magnetic heavy elements on the transient THz emission down to cryogenic temperatures. Furthermore, we will study the evolution of the THz emission characteristics due to interface intermixing of magnetic/non-magnetic bilayer spintronic THz emitters, by stepwise performing ion-irradiation in order to eventually create a homogenous magnetic alloy. Finally, we will study the impact of the chemical structure and distribution of the elements in a chemically ordered alloy on the THz emission.