Enhanced terahertz spin transmittance in the NiO/Pt structure through interface engineering

Since antiferromagnets (AFMs) have the potential to drive spintronic devices to higher speed and stability, generation, and transportation of terahertz (THz) spin currents in AFM/heavy metal (HM) structures have been extensively studied. However, effective methods to optimize the efficiency of THz spin current transmission at the interface are still lacking. Here, we demonstrated a significant enhancement of THz spin current in NiO/Pt structures by using THz emission spectroscopy. The spin transmittance is increased by up to a factor of 3.7 after heating the samples at a temperature of 350 °C for 0.5 h. This enhancement can be attributed to the optimization of the NiO/Pt interface resulting from the heating process. In contrast, the control samples NiO/Cu/Pt and NiO did not exhibit a similar enhancement, indicating that the improvement in spin current transmission is specific to the NiO/Pt interface. The scanning transmission electron microscopy is used to observe the optimized interface and confirmed the reason for THz signal enhancement. Our work paves a way for the modulation of AFM/HM interfaces and the optimization of ultrafast spintronic devices based on AFMs.