Temperature-tuned ferromagnetism in hydrogenated multilayer graphene.

Man Zhao,Jianfeng Jia,He Xiao,Shuai Chen,Tianjun Hu,Haishun Wu

doi:10.1039/c8ra02648c

Abstract

Improving the ferromagnetism properties of pure carbon-based materials is extremely important for their application in spintronics. Hydrogenation of graphene is an effective way to induce magnetic moment into graphene with the advantage of reversibility. However, little experimental work has been done to prove the effect of hydrogen on the magnetic properties of graphene so far, except for systems containing a large amount of oxygen or plasma-induced vacancy which complicated the magnetic origin. Here we report a facile electrochemical cathodic method to generate hydrogenated multilayer graphene or few-layer graphite using graphite powder as the raw material, and observed hydrogen-induced ferromagnetism in samples annealed at different temperatures. The observed results suggest that ferromagnetism of hydrogenated multilayer graphene can be tuned by high temperature treatment, which is attributed to a changeable relative amount of hydrogen atoms chemisorpted on two different sublattices during thermal treatment.

Highlights

Hydrogenation of graphene has attracted vast attention recently due to the possibility of tuning its mechanical, electronic, and magnetic properties in a reversible way
The observed results suggest that ferromagnetism of hydrogenated multilayer graphene can be tuned by high temperature treatment, which is attributed to a changeable relative amount of hydrogen atoms chemisorpted on two different sublattices during thermal treatment
The hysteresis loop measurement of the sample shows an obvious ferromagnetism signal at room temperature, more interestingly, our study reveals that the magnetism doesn't decrease when annealed at elevated temperature

Summary

Introduction

For multilayer graphene or few-layer graphite, theoretical studies show that the typical Bernal stacking of graphite planes effectively breaks sublattice symmetry, making two sublattices inequivalent from each other,[17,18] which reminds us to use hydrogenated multilayer graphene or few-layer graphite instead of few-layer graphene or single layer graphene as sample to tailor the magnetic properties of graphenic materials. The sample we achieved is almost free of structural vacancy and any other defects usually caused by oxidation. If these defects contribute to the magnetic moments, misinterpretation of the results might occur. Our sample could be a better candidate to study the magnetic properties of hydrogenated multilayer graphene. FTIR, TG-MS results suggest that different desorption rates of hydrogen atoms bonded on different sublattices through thermal annealing process is the main reason

Preparation of hydrogenated multilayer graphene

Results and discussion

Characterization

Conclusions