Large local Hall effect in pin-hole dominated multigraphene spin-valves

TL;DR

This study investigates the local Hall effect in multigraphene spin-valves with pin-hole tunnel barriers, revealing how barrier irregularities induce spurious signals and hinder spin-injection, especially at low temperatures.

Contribution

It demonstrates that local Hall effects caused by barrier roughness can mimic spin signals and impede spin-injection in multigraphene devices, providing insights into device optimization.

Findings

Local Hall effect causes spurious resistance switching.

Temperature increase reduces local Hall effect.

No spin signal observed in non-local measurements due to local Hall effect.

Abstract

We report local and non-local measurements in pin-hole dominated mesoscopic multigraphene spin-valves. Local spin-valve measurements show spurious switching behavior in resistance during magnetic field sweeping similar to the signal observed due to spin-injection into multigraphene. The switching behavior has been explained in terms of local Hall effect due to thickness irregularity of the tunnel barrier. Local Hall effect appears due to large local magnetostatic field produced at the roughness in the AlO$_x$ tunnel barrier. The effect of this local Hall effect is found to reduce as temperature is increased above 75 K. The strong local Hall effect hinders spin-injection into multigraphene resulting in no spin signal in non-local measurements.