Microstructure and magnetic properties of the (FePt)100-xCrx thin films

The (FePt)(100-x)Cr-x alloy thin films with x=0-16 at. % were fabricated on natural-oxidized Si(111) substrate by dc magnetron sputtering. The as-deposited films were annealed between 300 and 750 degrees C in order to transform the soft magnetic fcc gamma-FePt phase to the hard magnetic fct gamma(1)-FePt phase. The addition of Cr in the FePt thin films will reduce its saturation magnetization and coercivity, however, it could inhibit the grain growth during annealing of the samples. The optimum condition for high-density magnetic recording purpose of the (FePt)(100-x)Cr-x alloy films was found with x=5 at. %, annealing at 650 degrees C for 15 min, and ice water quench cooling. According to the transmission electron microscopy study, the average grain size in the annealed (FePt)(100-x)Cr-x alloy thin films decrease from 60 to 5 nm with increasing x from 0 to 16. (C) 2000 American Institute of Physics. [S0021-8979(00)52408-6].