Structure and magnetic properties of CoPt(FePt)-C nanocomposite films

CoPt(FePt)-C nanocomposite thin films were prepared by a pulsed filtered vacuum arc deposition technique. Thermal annealing was performed in vacuum at various temperatures. The dependence of the magnetic properties on the carbon fraction and annealing temperature was studied. Both x-ray diffraction and magnetic force microscopy analyses confirmed the formation of nano-crystallites of face-centered-tetragonal phase of CoPt or FePt in the carbon matrix after annealing at a sufficiently high temperature. For the film with particular compositions of Co24Pt31C45 and Fe43Pt35C22, the coercivity and the grain size were observed to increase with increasing annealing temperature. For the 6024 Pt31C45 film at an annealing temperature of 700°C, the coercivity was 2.1×105 A/m and the grain size was about 17 nm. For the Fe43Pt35C22 film at an annealing temperature of 650°C, the values were 2.8×105 A/m and 10.5 nm, respectively.