Absence of significant spin current generation in Ti/FeCoB bilayers with strong interfacial spin-orbit coupling

TL;DR

This study investigates whether interfacial spin-orbit coupling in Ti/FeCoB bilayers can generate significant spin currents, concluding that it does not, despite strong ISOC and enhanced magnetic anisotropy.

Contribution

The paper provides experimental evidence that strong interfacial spin-orbit coupling in Ti/FeCoB bilayers does not produce significant spin currents, challenging previous assumptions.

Findings

No significant charge-to-spin conversion observed.

Strong ISOC does not lead to spin current generation.

Minimal orbital Hall effect in Ti detected.

Abstract

After one decade of the intensive theoretical and experimental explorations, whether interfacial spin-orbit coupling (ISOC) at metallic magnetic interfaces can effectively generate a spin current has remained in dispute. Here, utilizing the Ti/FeCoB bilayers that are unique for the negligible bulk spin Hall effect and the strong tunable ISOC, we establish that there is no significant charge-to-spin conversion at magnetic interfaces via spin-orbit filtering effect or Rashba-Edelstein(-like) effect even when the ISOC is stronger than that of a typical Pt/ferromagnet interface and can promote strong perpendicular magnetic anisotropy. We also find a minimal orbital Hall effect in 3d Ti.