A study of the production techniques and magnetism of transition metal nanoparticles
[thesis]
Anwaar Ellahi Malik
2011
Magnetic elemental (Fe, Co, Ni) and alloy (Co-Pt, Ni-Pt, Fe-Pt, Co-Pt and Fe-Co-Pt) nanoparticles have been synthesized and studied for their potential applications in the development of high density data storage systems. Ion implantation and thermal annealing was used for the production and growth of nanoparticles in 100 nm silica layers thermally grown on (100) silica wafers. Transmission electron microscopy (TEM) and grazing incident X-ray diffraction (GIXRD) measurements confirmed the
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... icant effect of annealing temperature on the growth and crystal structure of nanoparticles. The size and distribution of elemental/alloy nanoparticles was found to depend on the particular element/s, even for chemically similar metals like Fe, Co and Ni. The high diffusivity of Fe was a major restriction for the formation of its elemental and alloy nanoparticles. However Co was suitable for forming larger elemental or alloy nanoparticles due to its ideal diffusivity in silica at 900oC. The addition of Pt was useful in reducing the high diffusivities of these metals. The room temperature magnetic measurements showed the dependence of size and composition of nanoparticles on their magnetic properties. Smaller nanoparticles (1.5 - 2 nm) were superparamagnetic, however in many cases a range of particle sizes were present and some ferromagnetic behaviour was also observed. Generally, the ferromagnetic behaviour enhanced with the increase in particle size. Although the Ni only and Ni based alloys (Co-Ni and Ni-Pt) nanoparticles with average sizes ~ 8.3 nm, ~ 10 nm and ~ 5.9 nm still exhibited superparamagnetism. Shape transformation of Co nanoparticles in silica was observed by irradiation of nanoparticles with 100 keV Pt ions. Irradiation induced damage effected the homogeneous Co-Pt alloy formation and resulted in the formation other compounds. The magnetic measurements demonstrated a significant difference in magnetic properties of Co-Pt alloy nanoparticles produced after irradiation of Co nanoparticles from the corresponding [...]
doi:10.26190/unsworks/15175
fatcat:afcpr65pbbavpfc7gyh3t7n3l4