The role of hydrogen in room-temperature ferromagnetism at graphite surfaces

TL;DR

This study reveals that hydrogen-mediated electronic states contribute to room-temperature ferromagnetism in graphite surfaces, showing intrinsic magnetism in metal-free samples due to hydrogen interactions.

Contribution

It demonstrates that hydrogen plays a key role in inducing ferromagnetism in graphite surfaces, an insight not previously established.

Findings

Hydrogen-mediated states exhibit spin polarization at room temperature.

Magnetization reaches approximately 15 emu/g in the top 10 nm of irradiated graphite.

Intrinsic ferromagnetism is confirmed in untreated, metal-free graphite.

Abstract

We present a x-ray dichroism study of graphite surfaces that addresses the origin and magnitude of ferromagnetism in metal-free carbon. We find that, in addition to carbon $\pi$ states, also hydrogen-mediated electronic states exhibit a net spin polarization with significant magnetic remanence at room temperature. The observed magnetism is restricted to the top $\approx$10 nm of the irradiated sample where the actual magnetization reaches $ \simeq 15$ emu/g at room temperature. We prove that the ferromagnetism found in metal-free untreated graphite is intrinsic and has a similar origin as the one found in proton bombarded graphite.