Anisotropic spin relaxation in graphene

TL;DR

This study investigates how spin relaxation times in graphene vary with spin orientation, revealing a 20% decrease for spins perpendicular to the plane, linked to anisotropic spin-orbit interactions.

Contribution

It provides experimental evidence of anisotropic spin relaxation in graphene and analyzes the role of spin-orbit effective fields in different directions.

Findings

20% decrease in spin relaxation time for out-of-plane spins

Spin relaxation is anisotropic depending on spin orientation

Results linked to differences in spin-orbit effective fields

Abstract

Spin relaxation in graphene is investigated in electrical graphene spin valve devices in the non-local geometry. Ferromagnetic electrodes with in-plane magnetizations inject spins parallel to the graphene layer. They are subject to Hanle spin precession under a magnetic field $B$ applied perpendicular to the graphene layer. Fields above 1.5 T force the magnetization direction of the ferromagnetic contacts to align to the field, allowing injection of spins perpendicular to the graphene plane. A comparison of the spin signals at B = 0 and B = 2 T shows a 20 % decrease in spin relaxation time for spins perpendicular to the graphene layer compared to spins parallel to the layer. We analyze the results in terms of the different strengths of the spin orbit effective fields in the in-plane and out-of-plane directions.