Contact Induced Spin Relaxation in Graphene Spin Valves with Al2O3 and MgO Tunnel Barriers

TL;DR

This study systematically compares contact-induced spin relaxation mechanisms in graphene spin valves with different tunnel barriers, revealing that effects beyond spin absorption dominate contact-related spin relaxation.

Contribution

It provides a detailed analysis distinguishing spin absorption from other contact-induced effects in graphene spin valves with MgO and Al2O3 barriers.

Findings

Contact-induced relaxation dominates over spin absorption.

Reasonable agreement between models for tunneling contacts.

Quantified discrepancies in spin lifetime estimates.

Abstract

We investigate spin relaxation in graphene by systematically comparing the roles of spin absorption, other contact-induced effects (e.g. fringe fields, etc.), and bulk spin relaxation for graphene spin valves with MgO barriers, Al2O3 barriers, and transparent contacts. We obtain effective spin lifetimes by fitting the Hanle spin precession data with two models that include or exclude the effect of spin absorption. Results indicate that additional contact-induced spin relaxation other than spin absorption dominates the contact effect. For tunneling contacts, we find reasonable agreement between the two models with median discrepancy of ~20% for MgO and ~10% for Al2O3.