Substrate Effect on Terahertz Emission in Fe/Pt Spintronic Emitters

The choice of the substrate plays an important role for spintronic terahertz (THz) emitters (STEs). We have grown epitaxial Pt/Fe bilayer thin films on MgO and MgAl
2
O
4
substrates. The THz electric field amplitude is found to be larger when Pt/Fe is grown on MgO even though the crystal quality of the Fe film is better when grown on MgAl
2
O
4
. This study indicates that the Fe crystal quality affects the THz emission in Pt/Fe STEs and points to the importance of a careful choice of the substrate to enhance the THz amplitude in STEs.