Found one research paper from 2014 on the magnetic properties of graphene oxide. It includes usage in vaccines causing defects in the graphene oxide which gives it magnetic properties.
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Magnetic graphene oxide, a compound of magnetic nanoparticles and graphene oxide, possesses distinct physical and chemical characteristics, including nano size, a large specific surface area, paramagnetic and biocompatible properties, making it a promising biomaterial in the field of biomedicine.
IOW, a compound with ferrous nanoparticulate material added to the graphene oxide....