Current-induced spin polarization on metal surfaces probed by spin-polarized positron beam.

H. J. Zhang,Y. Fukaya,T. Seki,A. Kawasuso,S. Yamamoto,E. Saitoh,K. Takanashi,M. Maekawa,H. Li

doi:10.1038/srep04844

Abstract

Current-induced spin polarization (CISP) on the outermost surfaces of Au, Cu, Pt, Pd, Ta, and W nanoscaled films were studied using a spin-polarized positron beam. The Au and Cu surfaces showed no significant CISP. In contrast, the Pt, Pd, Ta, and W films exhibited large CISP (3~15% per input charge current of 105 A/cm2) and the CISP of Ta and W were opposite to those of Pt and Pd. The sign of the CISP obeys the same rule in spin Hall effect suggesting that the spin-orbit coupling is mainly responsible for the CISP. The magnitude of the CISP is explained by the Rashba-Edelstein mechanism rather than the diffusive spin Hall effect. This settles a controversy, that which of these two mechanisms dominates the large CISP on metal surfaces.

Highlights

Correspondence and requests for materials should be addressed to Current-induced spin polarization on metal surfaces probed by spin-polarized positron beam
The sign of the Current-induced spin polarization (CISP) obeys the same rule in spin Hall effect suggesting that the spin-orbit coupling is mainly responsible for the CISP
The transversely spin-polarized positron beam, which was generated by a 22Na source (370 MBq) and an electrostatic apparatus, was implanted into the center of the sample14

Summary

Introduction

Correspondence and requests for materials should be addressed to Current-induced spin polarization on metal surfaces probed by spin-polarized positron beam. Current-induced spin polarization (CISP) on the outermost surfaces of Au, Cu, Pt, Pd, Ta, and W nanoscaled films were studied using a spin-polarized positron beam. The Pt, Pd, Ta, and W films exhibited large CISP (3,15% per input charge current of 105 A/cm2) and the CISP of Ta and W were opposite to those of Pt and Pd. The sign of the CISP obeys the same rule in spin Hall effect suggesting that the spin-orbit coupling is mainly responsible for the CISP. The magnitude of the CISP is explained by the Rashba-Edelstein mechanism rather than the diffusive spin Hall effect. This settles a controversy, that which of these two mechanisms dominates the large CISP on metal surfaces. -called giant Rashba effects (of the order of 100 meV) have been reported for bulk Ir[111]7, Bi/Ag[111] surface alloy, and Pb/Ag[111] surface alloy

Methods

Results

Conclusion