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

Area of Science:

• Spintronics
• Condensed Matter Physics
• Surface Science

Background:

• The Rashba-Edelstein effect facilitates charge-to-spin conversion.
• Direct observation of this effect in non-magnetic materials is challenging.
• Understanding spin dynamics at interfaces is crucial for spintronics.

Purpose of the Study:

• To directly observe charge-to-spin conversion via the Rashba-Edelstein effect in non-magnetic thin-film systems.
• To investigate the influence of layer order on surface spin polarization.
• To establish a novel technique for measuring spin diffusion length.

Main Methods:

• Fabrication of Bi/Ag/Al2O3 and Ag/Bi/Al2O3 heterostructures.
• Application of charge currents solely within the Ag layers.
• Utilizing a spin-polarized positron beam to probe surface electron spin polarization.

Main Results:

• Direct observation of surface spin polarization in non-magnetic Bi/Ag/Al2O3 and Ag/Bi/Al2O3 systems.
• Demonstration of opposite spin polarization directions for the two sample configurations under identical current.
• Exponential decay of spin polarization with outermost layer thickness, indicating spin diffusion.

Conclusions:

• The Rashba-Edelstein effect can induce observable spin polarization in non-magnetic materials.
• Layer arrangement significantly impacts the direction of induced spin polarization.
• The observed spin diffusion provides a new pathway for measuring spin diffusion length.