Spintronic GdFe/Pt THz emitters

We present a spintronic terahertz emitter based on a ferrimagnetic gadolinium-iron alloy (GdxFe1-x) and platinum (Pt). We measure the magnetic-field-dependent terahertz emission of GdxFe1-x/Pt spintronic heterostructures in the entire composition range (0 <= x <= 1). Excellent agreement is found between the measured data and a theoretical model based on the ratio of in-plane and saturation magnetization, up to a Gd content of x = 0.4 for all applied fields. At a higher Gd content (x >= 0.6), the measured terahertz amplitudes and the model deviate, due to the increasing influence of Gd. The GdxFe1-x/Pt emitters share similar properties with TbxFe1-x/Pt emitters, such as a strong increase in terahertz emission for a small rare earth content. However, our systematic study demonstrates that the terahertz emission amplitude of GdxFe1-x/Pt is up to 17 times higher than that of TbxFe1-x/Pt, which is important for the use and further optimization of these spintronic emitters operating at room temperature.