Growth and magnetism of Ni nanoparticles in Ni/Al2O3/Si or Si3N4 multilayers

We report on the fabrication of Ni/Al2O3/Si and textured Ni/Al2O3/Si3N4 multilayers containing Ni nanoparticles that exhibit significantly improved results. The secondary phases arising from thermal reaction between Ni and Si can be remarkably suppressed with increasing layers of Al2O3 and deposition of Ni/Al2O3 multilayers on Si3N4 substrates. Atomic force microscopy shows the formation of large as well as nanoclusters of Ni when grown on Si, whereas textured Ni nanoparticles are formed on Si3N4 substrates. The magnetization measurements on Ni/Al2O3/Si containing a single buffer layer of Al2O3 shows higher coercivity field with magnetic nanowire-like behavior, whereas with several Al2O3 alternate layers almost a superparamagnetic-like behavior is observed. However, significantly improved magnetic hysteresis was observed in textured Ni/Al2O3/Si3N4 multilayers due to preferred alignment of Ni nanocrystallites.