Charge-to-Spin Conversion and Spin Diffusion in Bi/Ag Bilayers Observed by Spin-Polarized Positron Beam

Abstract

Charge-to-spin conversion induced by the Rashba-Edelstein effect was directly observed for the first time in samples with no magnetic layer. A spin-polarized positron beam was used to probe the spin polarization of the outermost surface electrons of Bi/Ag/Al2O3 and Ag/Bi/Al2O3 when charge currents were only associated with the Ag layers. An opposite surface spin polarization was found between Bi/Ag/Al2O3 and Ag/Bi/Al2O3 samples with the application of a charge current in the same direction. The surface spin polarizations of both systems decreased exponentially with the outermost layer thickness, suggesting the occurrence of spin diffusion from the Bi/Ag interface to the outermost surfaces. This work provides a new technique to measure spin diffusion length.

Enhanced magneto-optical Kerr effect at Fe/insulator interfaces

“…To obtain large spin-orbit coupling, many different effects have recently been applied. These effects are as follows: spin-orbit splitting in the band structure due to the Rashba effect in systems without inversion symmetry [10][11][12] ; charge-spin conversions due to spin-momentum locking of topological surface states [13][14][15][16] ; Dzyaloshinskii-Moriya interactions in bilayer systems with heavy elements [17][18][19][20][21] ; spin-orbit couplings due to impurities [22][23][24][25][26][27] . There are a few ways to enhance the MOKE.…”

Spin-to-Charge Conversion in Bi Films and Bi/Ag Bilayers

“…Bismuth (Bi) is the heaviest non-radioactive element in the Periodic Table. It is natural to exploit the large SOC in Bi metal [19,20] and Bi-containing materials [21][22][23][24][25][26][27][28][29][30][31][32] for spin current phenomena. However, there are already conflicting results even in Bi metal and bilayers.…”

Rashba-Edelstein Magnetoresistance in Metallic Heterostructures

“…As shown in Figs. 1(a) and 1(b), a charge current carried by a two-dimensional electron gas with helical spin polarization is accompanied by a nonzero spin accumulation with the spins along the in-plane direction transverse to the applied charge current, which is known as the Rashba-Edelstein effect (REE) [19][20][21][22][23][24][25].…”