Synthesis and characterization of magnetic nanowires and magnetic thin films

The progress made by research activity performed worldwide in magnetism has led to exponential decay of magnetic device dimensions. Modern magnetic media stores almost 500 Gbit/in². One approach to extend this limit is to use the so called "nano magnet' in which one bit of information corresponds to one single domain nanosized particle. Since each bit would be composed of a single high-aspect particle, the areal density of these patterned media can, in principle, be much more than one order of magnitude higher than in conventional longitudinal media. Multilayer nanowires (an alternation of ferromagnetic and nonferromagnetic discs along a nanowire) arrays are promising nanostructures, especially for the application of giant magnetoresistance with current that is perpendicular to the plane. Incorporating magnetic material into on-chip inductors is one of the most researched approaches to increasing inductance density, quality factor Q and/or reduce capacitance, resistance and chip area. An on-chip inductor with magnetic material could give a significant boost to inductance density, and could reduce the size of inductors for single chip applications. Here different ferromagnetic nanowires and multilayer (Ni/Au,Co/Cu,Co/Au etc.) nanowires were synthesized and characterized. For ferromagnetic nanowires, diameter dependence magnetic characterization as well as MFM analysis on Ni nanowires were studied. For multilayer nanowires, the intrawire interactions in the arrays and the comparative magnetotransport study of different diameter Co/Cu multilayer nanowires were investigated. It was also demonstrated that the permeability of 1mum thick NiFe/Cr multilayer film can be tuned by varying the thickness of individual NiFe layer while keeping total multilayer film thickness constant. The results showed that the permeability can be increased from 170 to 650 by varying NiFe thicknesses from 100nm to 50nm, much higher than single layer NiFe of same thickness, with thinner NiFe layers having an inductance increase to a factor of 6.