  All-optical switching (AOS) of magnetic domains by femtosecond laser pulses
was first observed in the transition metal-rare earth (TM-RE) alloy GdFeCo1-5;
this phenomenon demonstrated the potential for optical control of magnetism for
the development of ever faster future magnetic recording technologies. The
technological potential of AOS has recently increased due to the discovery of
the same effect in other materials, including RE-free magnetic multilayers6,7.
However, to be technologically meaningful, AOS must compete with the bit
densities of conventional storage devices, restricting optically-switched
magnetic areas to sizes well below the diffraction limit. Here, we demonstrate
reproducible and robust all-optical switching of magnetic domains of 53 nm size
in a ferrimagnetic TbFeCo alloy using gold plasmonic antenna structures. The
confined nanoscale magnetic reversal is imaged around and beneath plasmonic
antennas using x-ray resonant holographic imaging. Our results demonstrate the
potential of future AOS-based magnetic recording technologies.
