3d-, 4d- and 5d-metal complexes as SIMs and SMMs MRI contrast agents Research & information: general adsorption drug delivery gadolinium oxide heavy metals hybrid iron oxide nanoparticles ligands magnetic domain visualization magnetic fluid hyperthermia magnetic hysteresis magnetic materials magnetic nanoparticles magnetic particle and nanoparticles magnetic particle toxicity magnetic resonance imaging magnetic resonance imaging (MRI), polymeric core–shells magnetic separation magnetic submicron core–shells magnetically-guided drug delivery systems magnetite nanoparticles magnetometry molecular magnetism multi-metal nanocomposite nanoparticles nanostructured materials nanotechnology