Large Orbital to Charge Conversion in Weak Spin Orbit Coupling Element Zr via Spin Orbital Pumping and Spin Orbital Seebeck Effect

TL;DR

This study demonstrates significant orbital to charge current conversion in Zr-based heterostructures with weak spin-orbit coupling, revealing new mechanisms for spintronic device efficiency enhancement.

Contribution

It uncovers the combined effects of spin and orbital currents in Zr heterostructures, highlighting the role of interfaces and layers in enhancing spin-orbital to charge conversion.

Findings

Enhanced effective spin-orbital Hall angle ({ heta}_eff) in Zr/Pt/CFB heterostructures.

Multiple contributions (ISHE, IOHE, IOREE) to spin-orbital to charge conversion.

Introduction of Pt layers significantly increases conversion efficiency.

Abstract

The generation of spin-orbital currents is crucial for advancing energy-efficient spintronic devices. Here, the intricate process involved in the generation and conversion of spin and orbital to charge currents in Zr(t=2, 3, 4.5, 6, &10nm)/Co60Fe20B20(CFB), Zr/Pt/CFB, and Zr/Pt/CFB/Pt heterostructures are investigated using spin-orbital pumping ferromagnetic resonance and longitudinal spin-orbital Seebeck effect measurements. The moderate spin-orbit coupling (SOC) in the CFB layer facilitates the simultaneous generation of spin and orbital currents, which are transferred into adjacent Zr and Pt layers. Different spin-orbital to charge current contributions, namely, Inverse spin Hall effect (ISHE), Inverse orbital Hall effect (IOHE), and Inverse orbital Rashba-Edelstein effect (IOREE) are analyzed. Notably, introducing a single Pt layer increases the spin-orbital to charge current conversion via combined effects: ISHE in Pt, IOREE in Zr/Pt interface. An enhanced effective spin-orbital Hall angle ({\theta}_eff) of 0.120 {\pm} 0.004 is observed for Zr/Pt/CFB, compared to that of 0.065 {\pm} 0.002 for the Zr/CFB, and 0.077 {\pm} 0.003 for the Zr/Pt/CFB/Pt heterostructures. These findings provide new insights into orbital-moment dependent phenomena and offer promising avenues for developing advanced spintronic devices exploiting both spin and orbital degrees of freedom, even in materials with lower SOC.