Enhancement of spintronic terahertz emission enabled by increasing Hall angle and interfacial skew scattering

Abstract

Spintronic terahertz (THz) emitters (STEs) based on magnetic heterostructures have emerged as promising THz sources. However, it is still a challenge to achieve a higher intensity STE to satisfy all kinds of practical applications. Herein, we report a STE based on Pt0.93(MgO)0.07/CoFeB nanofilm by introducing dispersed MgO impurities into Pt, which reaches a 200% intensity compared to Pt/CoFeB and approaches the signal of 500 μm ZnTe crystal under the same pump power. We obtain a smaller spin diffusion length of Pt0.93(MgO)0.07 and an increased thickness-dependent spin Hall angle relative to the undoped Pt. We also find that the thickness of a Pt layer leads to a drastic change in the interface role in the spintronic THz emission, suggesting that the underlying mechanism of THz emission enhancement is a combined effect of enhanced bulk spin hall angle and the interfacial skew scattering by MgO impurities. Our findings demonstrate a simple way to realize high-efficiency, stable, advanced spintronic THz devices.