| In this work, we have prepared thin film CoPt and FePt magnetic grains embedded in nonmagnetic matrices of C, Cu and Ag by a pulsed filtered vacuum arc deposition technique, and investigated their properties and potential as recording media for ultra-high density magnetic recording applications.; For CoPt-C nanocomposite films, the results show that the grain size and coercivity strongly depend on the C concentration and annealing temperature. The higher C concentration film, Co16Pt24C60, can achieve a smaller grain size. However, a relatively higher annealing temperature (≥700°C) is required for the grains to grow in size, to achieve the fcc-fct phase transformation and to obtain a large coercivity. For the lower C concentration film, Co37Pt51C12, the grains grow rapidly with increasing annealing temperature, up to 21 nm at 650°C, causing multi-domain structure formation in the film, resulting in a decrease in the Hc. For the Co24Pt31C45 films, both x-ray diffraction and magnetic force microscopy analyses confirmed the formation of nano-crystallites of face-centred-tetragonal (fct) CoPt phase in the carbon matrix when the annealing temperature was higher than 600°C, resulting in coercivities up to 7 kOe and with the grain size within the range of 9--20 nm.; On the other hand, we have also prepared FePt-X (X = C, Cu, or Ag) nanocomposite films by two different preparation methods. The first one used a co-deposition process together with vacuum annealing. The other one used a multilayer deposition process plus rapid thermal annealing. Compared with the co-deposited CoPt-C films, the co-deposited FePt-C films can achieve a reduction in the L10 ordering temperature down to 500°C, with a grain size of 12.5 nm, a larger Hc of 7.5 kOe and a higher Ms of 700 emu/cm3. The influence of C, Cu, and Ag additives on the L10 ordering and grain growth of the multilayer-deposited FePt films has been investigated. The results show that with Cu additive, the ordering temperature can be reduced down to 300°C. The most effective Cu content for reducing the ordering temperature is around 12 at.%. The results also suggest that the formation of FePtCu alloy in the films may have played an important role in accelerating the ordering process. (Abstract shortened by UMI.)... |
