Asymmetric nano graphene model applied to graphite-like room-temperature ferromagnetism

TL;DR

This paper models asymmetric graphene molecules to explain room-temperature ferromagnetism in graphite-like materials, revealing how edge asymmetry and nitrogen doping contribute to magnetic properties.

Contribution

It introduces a novel molecular model using semi-empirical and first-principles methods to explain ferromagnetism in carbon-based materials at room temperature.

Findings

Asymmetric dihydrogenated graphene edges favor high spin states.

Proton irradiation induces asymmetric features leading to ferromagnetism.

Nitrogen doping in graphite can be explained by similar asymmetric molecular models.

Abstract

Room temperature ferromagnetic materials composed only by light elements like carbon, hydrogen and/or nitrogen, so called carbon magnet, are very attractive for creating new material categories both in science and industry. Recently several experiments suggest ferromagnetic features at a room temperature, especially in graphite base materials. This paper reveals a mechanism of such ferromagnetic features by modeling nanometer size asymmetric graphene molecule by using both a semi-empirical molecular orbital method and a first principle density function theory. Asymmetrically dihydrogenated zigzag edge graphene molecule shows that high spin state is more stable in total molecular energy than low spin state. Proton ion irradiation play an important role to create such asymmetric features. Also, nitrogen contained graphite ferromagnetism is explained by a similar asymmetric molecule model.