Assembly of superparamagnetic nanoparticles under unidirectional external magnetic flux: Experimental and model establishments

Recent development in assembling nanoparticles as building blocks into macroscopic functional structures or devices to harness the size-dependent properties of individual particles is an exciting new direction. Here, it is demonstrated that well-dispersed silica- encapsulated superparamagnetic FePt nanoparticles in solution can be assembled into high-quality, needle- or rod-shaped solid-state supercrystals by applying inhomogeneous external magnetic field together with controlled evaporation. By use of an aggregation model based on the population balance equation technique, this charactersitic morphology of the magnetic asembled crystals can be successfully derived.