Combined reactions associated with L10 ordering

Recently, self-organized magnetic arrays (SOMAs) have received a great deal of attention because of the potential of achieving magnetic data storage densities greater than 1 Tbit/in(2). SOMA involves the chemical preparation of self-assembled arrays of alloyed nanoparticles (such as FePt), which can be subsequently annealed to form an L1(0) high magnetocrystalline anisotropy chemically ordered phase. However, during the anneal of the nanoparticles the system can further lower its energy by the elimination of surface area which is brought about by another solid-state reaction which is sintering. Therefore, the combined reactions of ordering and sintering must be understood in a systematic way. Previous work on L1(0) bulk alloys are reviewed with particular emphasis on the role of combined reactions such as ordering and recrystallization. A methodology is described to help in the understanding of combined reactions involving ordering and solid-state reactions concerning the elimination of crystalline defects such as dislocations, grain boundaries and external surfaces. As a first attempt, this framework based on bulk solid-state reactions is developed and further discussed for the case of SOMA nanoparticles. (C) 2003 Elsevier B.V. All rights reserved.