Investigation of Spin-Current Lifetime in Fe/Pt Spintronic Terahertz Emitter using Double Optical Pump Technique

The spin current lifetime of Fe/Pt spintronic terahertz emitters (STE’s) were investigated using a double-optical pump (DOP) terahertz time-domain spectroscopy scheme. One of the spintronic terahertz emitters had a patterned diabolo-shaped structure on the surface while the other spintronic emitter was a standard bilayer heterostructure. Finally, the current lifetimes of the two STEs were compared with a conventional LT-GaAs bowtie photoconductive antenna. The resulting DOP signals were curve fitted with an exponential function yielding time constants of τdiabolo = 390 fs, τFe/Pt = 140 fs, and τLT-GaAs = 2.6 ps.