Limits on intrinsic magnetism in graphene

TL;DR

This study investigates the magnetic properties of graphene nanocrystals, finding no ferromagnetism or strong paramagnetism, and revealing that graphene is predominantly diamagnetic with only weak paramagnetic contributions at low temperatures.

Contribution

The paper provides the first detailed experimental analysis showing the absence of ferromagnetism in graphene nanocrystals and identifies the nature of defect-related paramagnetism.

Findings

Graphene nanocrystals are strongly diamagnetic.

No ferromagnetism detected down to 2 K.

Weak paramagnetism linked to defect sites.

Abstract

We have studied magnetization of graphene nanocrystals obtained by sonic exfoliation of graphite. No ferromagnetism is detected at any temperature down to 2 K. Neither do we find strong paramagnetism expected due to the massive amount of edge defects. Rather, graphene is strongly diamagnetic, similar to graphite. Our nanocrystals exhibit only a weak paramagnetic contribution noticeable below 50K. The measurements yield a single species of defects responsible for the paramagnetism, with approximately one magnetic moment per typical graphene crystallite.