Pattern formation in an array of magnetic nanoscale rods mimics magnetic-dipole interaction-driven spinodal decomposition

Magnetic-field-assisted self-assembly of magnetic-dipole moment carrying aerosol-grown iron nanoparticles on a nonmagnetic substrate results in the formation of magnetic nanoscale rods and bundles thereof. The magnetic dipolar interaction between the bundles essentially drives the formation of regular patterns of bundle density modulations in the two-dimensional array of elastically deformable magnetic rods. This pattern formation is shown to belong to the class of physical systems undergoing spinodal decomposition. Possible applications for dipolar magnetic nanorods in the fields of perpendicular storage media and ferrofluids are highlighted. A giant magnetoviscous effect is expected.