Magnetic Moment Formation in Graphene Detected by Scattering of Pure Spin Currents

TL;DR

This study demonstrates that hydrogen adatoms and lattice vacancies in graphene induce magnetic moments, affecting spin transport by scattering pure spin currents and generating exchange fields, confirmed through spin valve and Hanle measurements.

Contribution

It provides direct experimental evidence of magnetic moment formation in graphene due to adatoms and vacancies, linking defect-induced magnetism to spin transport phenomena.

Findings

Hydrogen adatoms cause a dip in non-local spin signals.

Magnetic moments generate an exchange field affecting spin precession.

Defects like vacancies also induce magnetic moments.

Abstract

Hydrogen adatoms are shown to generate magnetic moments inside single layer graphene. Spin transport measurements on graphene spin valves exhibit a dip in the non-local spin signal as a function of applied magnetic field, which is due to scattering (relaxation) of pure spin currents by exchange coupling to the magnetic moments. Furthermore, Hanle spin precession measurements indicate the presence of an exchange field generated by the magnetic moments. The entire experiment including spin transport is performed in an ultrahigh vacuum chamber, and the characteristic signatures of magnetic moment formation appear only after hydrogen adatoms are introduced. Lattice vacancies also demonstrate similar behavior indicating that the magnetic moment formation originates from pz-orbital defects.