Investigation and Optimization of Terahertz Emission in Co20Fe60B20‐Based Spintronic Trilayer Structures

Spintronic terahertz (THz) sources, represented by Co 80–x Fe x B 20 ‐based heterostructures, have garnered significant attention due to their ability to efficiently generate THz radiation and the flexibility in device structure. Herein, spintronic THz emitters based on nonmagnetic/ferromagnetic/nonmagnetic (NM/FM/NM) metal heterostructures, with Co 20 Fe 60 B 20 (CFB) designed as the FM layers, are fabricated. The THz emission properties of the trilayer spintronic emitters are investigated experimentally, providing insights into the effects of material combinations (Ta or Pt), layer thicknesses, pump fluence, and magnetization of FM layer on THz generation. Specifically, since the spin Hall angles of Pt and Ta have opposite signs and thereby the parallel spin‐Hall currents in these two layers radiate THz wave in phase, it is found that the Pt/CFB/Ta structure can effectively generate THz wave with a maximum bandwidth of ≈2.45 THz. The pump fluence and FM (NM) thickness dependencies of the THz peak amplitude and bandwidth are obtained. Moreover, using different external magnetic fields for magnetization, the direction of the net/intrinsic spin polarization in the CFB layer is determined. These results can provide detailed knowledge about the THz emission properties of CFB‐based spintronic devices, and one can find applications in the optimization of such kind of THz emitters.