Anisotropic Elliott-Yafet Theory and Application to KC$_8$ Potassium Intercalated Graphite

TL;DR

This paper investigates the anisotropic spin-relaxation in potassium intercalated graphite using ESR measurements, applying an anisotropic Elliott-Yafet theory to understand the spin-orbit interactions in layered materials.

Contribution

It introduces an anisotropic Elliott-Yafet model for layered materials and applies it to interpret ESR measurements in KC$_8$, linking experimental data with first-principles spin-orbit theories.

Findings

Spin-lattice relaxation time is longer when magnetic field is perpendicular to graphene layers.

The anisotropic Elliott-Yafet theory successfully explains the observed ESR anisotropy.

Provides experimental input for first-principles spin-orbit interaction models in layered carbon materials.

Abstract

We report Electron Spin Resonance (ESR) measurements on stage-I potassium intercalated graphite (KC$_8$). Angular dependent measurements show that the spin-lattice relaxation time is longer when the magnetic field is perpendicular to the graphene layer as compared to when the magnetic field is in the plane. This anisotropy is analyzed in the framework of the Elliott-Yafet theory of spin-relaxation in metals. The analysis considers an anisotropic spin-orbit Hamiltonian and the first order perturbative treatment of Elliott is reproduced for this model Hamiltonian. The result provides an experimental input for the first-principles theories of spin-orbit interaction in layered carbon and thus to a better understanding of spin-relaxation phenomena in graphene and in other layered materials as well.