CoPt and FePt thin films for high density recording media

Highly anisotropic face-centered-tetragonal (fct) CoPt and fct FePt nanopar ticles have been prepared and embedded in a C or BN matrix by cosputtering from pure Co50Pt50, BN, and Fe50Pt50, C solid targets using a tandem deposi tion mode. The as-made films show a disordered face-centered-cubic structur e which is magnetically soft and have low coercivity (< 20 Oe). Magnetic ha rdening occurs after heat treatment at elevated temperatures, which leads t o increase in coercivity to values up to 15 kOe at room temperature. The ha rdening is due to the formation of nanoparticles with the highly anisotropi c fct with anisotropy K > 10(7) erg/cm(3). Transmission electron microscope studies showed FePt particles embedded in C matrix with a size increasing from below 3 nm in the as-made state to about 8 nm in the optimum annealed state. These results are very promising and make these materials potential candidates for high-density magnetic recording. (C) 2000 American Institute of Physics. [S0021-8979(00)46508-4].