THz pulses from optically excited Fe, Pt and Ta based Spintronic Heterostructures

TL;DR

This paper reviews the use of spintronic heterostructures, especially Fe, Pt, and Ta based, as efficient broadband THz sources, highlighting recent experimental improvements in THz emission strength.

Contribution

It reports new experimental results showing enhanced THz emission from specific Fe, Pt, and Ta heterostructures, advancing the understanding of their efficiency.

Findings

Ta/Fe/Pt tri-layer generates 40-250% stronger THz signals.

Optimization of heterostructure parameters improves THz emission.

Inverse spin Hall effect is key to THz pulse generation.

Abstract

Spintronic heterostructures are considered to be the new generation THz sources for their capability in producing high power and broadband THz radiation. Here, we provide a brief review on the state-of-the-art in this field. The optically excited bi- and tri-layer combinations of ferromagnetic and nonmagnetic thin films have become increasingly popular. Towards optimizing the THz conversion efficiency and broadband gapless spectrum from these THz emitters, various control parameters need to be taken into consideration. The inverse spin Hall effect in the heavy metal layer of the heterostructure is primarily responsible for the generation of THz pulses. A few new results on iron, platinum and tantalum based heterostructures have also been reported here. It is observed that the Ta(2nm)/Fe(2nm)/Pt(2nm) tri-layer heterostructure generates ~40(250)% stronger THz signal as compared to the counterpart Fe(2nm)/Pt(2nm) (Fe(3nm)/Ta(2nm)) bi-layer heterostructure.