Spin mediated enhanced negative magnetoresistance in Ni80Fe20 and p-silicon bilayer

TL;DR

This study demonstrates that spin polarization via the spin-Hall effect enhances negative magnetoresistance in a Ni80Fe20/p-Si bilayer, with experimental evidence showing increased resistance reduction compared to Ni80Fe20 alone.

Contribution

The paper introduces experimental evidence of spin-Hall effect mediated spin polarization causing enhanced negative magnetoresistance in Ni80Fe20/p-Si bilayers, a novel observation in such systems.

Findings

Resistance decreases by ~2.5% in bilayer under magnetic field.

Spin polarization reduces hole-phonon scattering.

Sinusoidal behavior of V2ω and V3ω indicates spin-Hall effect involvement.

Abstract

In this work, we present an experimental study of spin mediated enhanced negative magnetoresistance in Ni80Fe20 (50 nm)/p-Si (350 nm) bilayer. The resistance measurement shows a reduction of ~2.5% for the bilayer specimen as compared to 1.3% for Ni80Fe20 (50 nm) on oxide specimen for an out-of-plane applied magnetic field of 3T. In the Ni80Fe20-only film, the negative magnetoresistance behavior is attributed to anisotropic magnetoresistance. We propose that spin polarization due to spin-Hall effect is the underlying cause of the enhanced negative magnetoresistance observed in the bilayer. Silicon has weak spin orbit coupling so spin Hall magnetoresistance measurement is not feasible. We use V2{\omega} and V3{\omega} measurement as a function of magnetic field and angular rotation of magnetic field in direction normal to electric current to elucidate the spin-Hall effect. The angular rotation of magnetic field shows a sinusoidal behavior for both V2{\omega} and V3{\omega}, which is attributed to the spin phonon interactions resulting from the spin-Hall effect mediated spin polarization. We propose that the spin polarization leads to a decrease in hole-phonon scattering resulting in enhanced negative magnetoresistance.