A magnetic graphene-like nanoparticle or graphitic nano- or microparticle exhibits a high relaxivity, and is useful as a MRI contrast agent. A composition for use with MRI imaging, comprising a sufficient amount of the magnetic graphene-like nanoparticles or graphitic nano- or microparticles and one or more physiologically acceptable carriers or excipients. Methods of using the magnetic graphene-like nanoparticles or graphitic nano- or microparticles as MRI contrast agents. Methods of producing the magnetic graphene-like nanoparticle or graphitic nano- or microparticle.
