Cobalt was electrodeposited onto chemical vapor deposition (CVD) graphene/Si/SiO2 substrates, during different time intervals, using an electrolyte solution containing a low concentration of cobalt sulfate. The intention was to investigate the details of the deposition process (and the dissolution process) and the resulting magnetic properties of the Co deposits on graphene. During and after electrodeposition, in-situ magnetic measurements were performed using an (AGFM). These were followed by ex situ morphological analysis of the samples with ΔtDEP 30 and 100 s by atomic force microscopy in the non-contact mode on pristine CVD graphene/SiO2/Si. We demonstrate that it is possible to electrodeposit Co onto graphene, and that in-situ magnetic measurements can also help in understanding details of the deposition process itself. The results show that the Co deposits are ferromagnetic with decreasing coercivity (HC) and demonstrate increasing magnetization on saturation (MSAT) and electric signal proportional to remanence (Mr), as a function of the amount of the electrodeposited Co. It was also found that, after the end of the dissolution process, a certain amount of cobalt remains on the graphene in oxide form (this was confirmed by X-ray photoelectron spectroscopy), as suggested by the magnetic measurements. This oxide tends to exhibit a limited asymptotic amount when cycling through the deposition/dissolution process for increasing deposition times, possibly indicating that the oxidation process is similar to the graphene surface chemistry.

• Vinícius C. De Franco(Institute of Physics, Federal University of Rio Grande do Sul, Porto Alegre 91501-970, Brazil. Materials Science Graduate Program, Federal University of Rio Grande do Sul, Porto Alegre 91501-970, Brazil) Corresponding Author
• Gustavo M. B. Castro(Natural Sciences Center, State University of Piauí, Teresina 64002-150, Brazil)
• Jeaneth Corredor(Institute of Physics, Federal University of Rio Grande do Sul, Porto Alegre 91501-970, Brazil)
• Daniel Mendes(Institute of Physics, Federal University of Rio Grande do Sul, Porto Alegre 91501-970, Brazil)
• João E. Schmidt(Institute of Physics, Federal University of Rio Grande do Sul, Porto Alegre 91501-970, Brazil)