Role of MgO barriers for spin and charge transport in Co/MgO/graphene non-local spin-valve devices

TL;DR

This study explores how MgO barriers influence spin and charge transport in Co/MgO/graphene non-local spin-valve devices, revealing contact resistance effects on spin lifetime and charge transport characteristics.

Contribution

It demonstrates the impact of contact resistance on spin lifetime and uncovers the presence of a second Dirac peak due to charge transport under contacts.

Findings

Inverse relation between spin lifetime and mobility in high-resistance devices

Presence of a second Dirac peak in devices with long spin lifetimes

Reduced spin lifetime under low-resistance contacts

Abstract

We investigate spin and charge transport in both single and bilayer graphene non-local spin-valve devices. Similar to previous studies on bilayer graphene, we observe an inverse dependence of the spin lifetime on the carrier mobility in our single layer devices. This general trend is only observed in devices with large contact resistances. Furthermore, we observe a second Dirac peak in devices with long spin lifetimes. This results from charge transport underneath the contacts. In contrast, all devices with low ohmic contact resistances only exhibit a single Dirac peak. Additionally, the spin lifetime is significantly reduced indicating that an additional spin dephasing occurs underneath the electrodes.