In one general approach, a product includes an underlayer of a magnetic recording medium. The underlayer has encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an aromatic polymer, and a polymeric binder binding the encapsulated nanoparticles. A magnetic recording layer is formed above the underlayer. In another general approach, a product includes an electrically conductive underlayer of a magnetic recording medium. The underlayer has encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an aromatic polymer, and a polymeric binder binding the encapsulated nanoparticles. A magnetic recording layer is formed above the underlayer. The magnetic nanoparticles have an average magnetic field strength of less than 200 Oersted (Oe). An average concentration of the encapsulated nanoparticles in the underlayer is at least 35 vol %.