Fig. 6

a Hysteresis loop measured at 300 K of densely packed 2D self-assembled Fe nanoparticle arrays, showing that the nanoparticles are in the superparamagnetic states. b TEM image of TiN nanoparticle arrays deposited on a TEM grid covered by amorphous carbon film, showing that the nanoparticle arrays are composed of domains of ordered densely packed 2D monolayers