Fabrication of superparamagnetic permalloy nanostructures in ZnO matrix by ion beam sputtering

Abstract Dipolar interactions among superparamagnetic nanoparticles lead to interesting phenomena such as superspin glass and superferromagnetism that are of interest in fabricating novel spintronic devices. This work investigates the occurrence of such phenomena in magnetic thin film stacks composed of permalloy-80 and ZnO thin films synthesized by ion beam sputtering. Particle induced X-ray emission was used to measure the composition of the thin film stacks. Atomic force microscopy revealed the changes in surface topography with composition. Detailed investigations were carried out to study the magnetic properties. Temperature-dependent magnetization measurement confirmed that the thin film stacks follow Bloch T3/2 law and the Curie temperature of the stacks was determined to lie between 620 and 670 K. Zero-field cooled and field cooled measurements identified the presence of superparamagnetic nanoparticles in the stack. Field dependent magnetization measurements were further carried out at different temperatures to identify and reveal the nature of dipolar interactions among the nanoparticles. The preliminary investigation carried out in this work confirms the possibility of fabricating a magnetic semiconductor system composed of interacting superparamagnetic nanoparticles by ion beam sputtering.