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Effect of annealing on the structure and magnetic properties of graphite encapsulated nickel and cobalt nanocrystalsLarge area arrays of cobalt and nickel particles with truncated conical shapes and diameters of 80-120 nm have been prepared using interference lithography combined with an evaporation and lift-off process. The magnetic hysteresis has been measured and the remanent states of the particles have been compared with a three-dimensional micromagnetic model. The model shows a transition from ''flower'' to ''vortex'' magnetization states as the particle size increases. The distribution of switching fields and the magnetostatic interactions between particles have been characterized. Both lead to a slow approach to saturation in the hysteresis loops. The suitability of such arrays for data storage is discussed.