Synthesis of Fe₃O₄ nanostructures by backward plume deposition and influence of ambient gas pressure on their morphology

Iron oxide nanostructures with significantly fewer droplets were successfully synthesized by pulsed laser deposition using a special target-substrate geometry, which is coined backward plume deposition. The morphology of deposited nanostructures for backward plume deposition is found to be strongly controlled by the ambient gas pressure and changes from a thin film to an assemble of nanoclusters to nanoclusters with loosely bound floccule-like network with the increase in ambient gas pressure. The post-annealing considerably changes the structural properties of deposited materials, which were determined to be magnetite FCC-Fe₃O₄. It also causes the relaxation of long range stress in the film and hence leads to an increase in the saturation magnetization. The coercivity is found to decrease upon annealing due to the growth of randomly oriented Fe₃O₄ nanocrystallite as well as the relaxation of internal stress.