Correlation of interface transmission in THz spintronic emitters with spin mixing conductance in spin pumping experiments

TL;DR

This paper investigates how the efficiency of THz spintronic emitters relates to interface properties, specifically spin mixing conductance, revealing that better epitaxial interfaces enhance both spin current transport and THz emission.

Contribution

It demonstrates a correlation between spin mixing conductance and THz emission, suggesting interface engineering can improve spintronic THz emitter performance.

Findings

Higher epitaxy improves spin mixing conductance.

Enhanced spin mixing conductance correlates with increased THz emission.

Interface quality critically affects spin current transport.

Abstract

The field of THz spintronics is a novel direction in the research field of spintronics that combines magnetism with optical physics and ultrafast photonics. The experimental scheme of the field involves the use of femtosecond laser pulses to trigger ultrafast spin and charge dynamics in bilayers composed of ferromagnetic (FM) and non-magnetic (NM) thin films where the NM layer features a strong spin-orbit coupling. The key technological and scientific challenges of THz spintronic emitters is to increase their intensity and frequency bandwidth. To achieve this the control of the source of the radiation, namely the transport of the ultrafast spin current is required. However, the transfer of a spin current from a FM to a NM layer is a highly interface-sensitive effect. In this work we study the properties of the spin current transport through the interface measuring the strength of the THz emission and compare it to the effective spin mixing conductance, one of the key concepts in the spin current transport through interfaces. The results show an enhancement of the spin mixing conductance for interfaces with higher degree of epitaxy similarly to the improvement of the THz emission. The proportionality between spin mixing conductance and THz emission can define new directions in engineering the emission of spintronic THz emitters.