Characterization of magnetic nanocomposite thin films for high density recording prepared by pulsed filtered vacuum arc deposition.

摘要

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.)