  We introduce a theoretical framework to describe the heat flux radiated in
the near-field regime by a set of magneto-optical thermal nanoemitters close to
a substrate in the presence of an external magnetic field. Then, we investigate
the particular case of a single emitter and we demonstrate that the external
field can induce both an amplification of the heat exchanged between emittter
and substrate and a focusing of the Poynting field at the substrate interface
at deep sub-wavelength scale. These effects open up promising perspectives for
the development of heat-assisted magnetic-recording technology.
