Defect-induced ferromagnetism in graphite

TL;DR

This paper provides direct evidence of room-temperature ferromagnetism in defect structures of graphite, attributed to unpaired electron spins at grain boundaries, excluding magnetic impurities as the cause.

Contribution

It demonstrates intrinsic ferromagnetism in graphite due to defect-induced localized electron spins, confirmed by magnetic force microscopy and spectroscopy.

Findings

Ferromagnetic order observed at room temperature in graphite

Magnetic impurities excluded as the source of magnetism

Localized states at grain boundaries linked to ferromagnetism

Abstract

We demonstrate direct evidence for ferromagnetic order at defect structures in highly oriented pyrolytic graphite with magnetic force microscopy at room temperature. Magnetic impurities have been excluded as the origin of the magnetic signal after careful analysis supporting an intrinsic magnetic behavior of carbon-based materials. The observed ferromagnetism has been attributed to originate from unpaired electron spins localized at grain boundaries. Scanning tunneling spectroscopy of grain boundaries showed intense localized states and enhanced charge density compared to bare graphite.