EPR study of nano-structured graphite

TL;DR

This study uses temperature-dependent EPR to analyze nano-structured graphite, revealing edge states, exchange interactions, and magnetic correlations that evolve with aging, providing insights into its electronic and magnetic properties.

Contribution

It presents the first systematic EPR analysis of nano-sized graphite, highlighting the effects of aging and structural changes on magnetic properties.

Findings

EPR resonance at g=2.0035 observed in as-prepared samples

EPR linewidth exhibits Korringa-like linear temperature dependence

EPR spin susceptibility peaks at ~23 K indicating antiferromagnetic correlations

Abstract

We report on a systematic temperature dependent X-band electron paramagnetic resonance (EPR) study of nano-sized graphite particles prepared by ball-milling. In as-prepared samples a very intense and sharp EPR resonance at $g=2.0035$ has been measured. The EPR linewidth shows a Korringa-like linear temperature dependence arising due to the coexistence and strong exchange coupling of itinerant and localized edge states. With a prolonged aging in inert atmosphere changes in the EPR signal suggest gradual structural reconstruction where the localized edge-states dominate the EPR signal. In this case the EPR spin susceptibility shows a maximum at $\approx 23\, {\rm K}$ indicating the development of antiferromagnetic correlations as expected for the graphene lattice with a bipartite symmetry.