Vertical Spin Transport in Al with Pd/Al/Ni80Fe20 Trilayer Films at Room Temperature by Spin Pumping

TL;DR

This study demonstrates room-temperature vertical spin transport in Al using spin pumping in a Pd/Al/Ni80Fe20 trilayer, revealing a short spin coherence length influenced by interface roughness.

Contribution

It introduces a simple model to estimate spin coherence length in Al during vertical spin transport, highlighting the impact of interface roughness on spin pumping efficiency.

Findings

Spin current flows through Al to Pd, generating electromotive forces via inverse spin Hall effect.

The spin coherence length in Al is estimated at 61 nm.

Interface roughness reduces spin pumping efficiency.

Abstract

Spin pumping enables the vertical transport of pure spin current through Al in a Pd/Al/Ni80Fe20(Py) trilayer film, in which the Py acts as a spin battery. The spin current injected into the Al flows through the Al to reach the Pd, resulting in the generation of electromotive forces due to the inverse spin Hall effect in the Pd. The electromotive forces decreased with increasing thickness of the Al layer. A simple model based on the theory by Tserkovnyak et al., [Phys. Rev. B, 66, 224403 (2002)] allows an estimation of the spin coherence of the perpendicular spin transport in the Al of 61 nm. This comparatively short coherence is attributed to a reduction in spin pumping efficiency because of the roughness of the Al/Py interface.