Effect of defects controlled by preparation condition and heat treatment on the ferromagnetic properties of few-layer graphene

Qinghua Miao,Xiangli Liu,Bing Wei,Weidong Fei,Lidong Wang,Jinhui Wang,Zhaoyuan Liu

doi:10.1038/s41598-017-06224-w

Qinghua Miao, Xiangli Liu + Show 5 more

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https://doi.org/10.1038/s41598-017-06224-w

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Abstract

Magnetism in graphene has stimulated extensive studies to search for novel metal-free magnetic device. In this paper, we use a synthesis method far from equilibrium state named self-propagating high temperature synthesis (SHS) to produce few-layer graphene with different defect contents and then use a heat treatment process (vacuum-annealing and air-cooling) to further control the defects in graphene. We find that the type and content of defects in graphene can be controlled by adjusting the mole ratio of reactants (Mg: CaCO3) for SHS reaction and the temperature of the subsequent heat treatment. The deviation of the ratio of reactants from stoichiometric ratio benefits the production of graphene with higher concentration of defects. It is indicated that the temperature of the heat treatment has remarkable influences on the structure of graphene, Raman-sensitive defects can be recovered partly by heat treatment while IR-sensitive defects are closely related with the oxidation and decomposition of the oxygen-containing groups at elevated temperature. This work indicates that SHS is a promising method to produce graphene with special magnetism, and the heat treatment is an effective way to further adjust the magnetism of graphene. This work sheds light on the study to develop carbon materials with controlled ferromagnetism.

Highlights

Graphene has generated a lot of activity in the area of material science due to its exceptional electronic and mechanical properties[1, 2]
Ferromagnetism has been observed in graphene materials prepared by different methods like thermal exfoliation of graphitic oxide, conversion of nano diamonds, arc evaporation of graphite in hydrogen and graphene oxide partially reduced by hydrazine and further completely reduced by thermal annealing, since graphene obtained by different methods has different types and quantity of defects[13]
Our works indicated that the deviation of stoichiometric ratio of the reactants under far from equilibrium state is a promising method to produce graphene with special magnetism, and that the designed heat treatment is an effective way to further adjust the ferromagnetism of graphene

Summary

Result and Discussion

In order to obtain more detailed information, the contents of components in C 1 s of M2C1 and M4C1 treated at different temperatures are analyzed according to the fitting and the results are shown in the Fig. 3(b,c,d and e). Comparing the ratios of the samples treated by different temperatures, we can find that the ratios of I2D/IG for M2C1 and M4C1 at any treated temperatures do not change significantly, which indicates that the heating treatment has no obvious effect on the number of graphene layers. Based on the analyses above-mentioned, we obtain a more comprehensive scene of the magnetism properties of the SHS graphene and the effect of heat treatment on them Both Raman-sensitive and FTIR-sensitive defects could contribute to the ferromagnetic properties of graphene. The heat treatment plays an important role on elucidating the effect of different factors for the ferromagnetism of graphene

Conclusions

Findings

Author Contributions

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