FePt thin films with 40 nm thickness were prepared on thermally oxidized Si (001) substrates by dc magnetron sputtering at the nominal growth temperature 375 degrees C. The effects of annealing on microstructure and magnetic properties of FePt thin films were investigated. The as-deposited FePt thin films show soft magnetic properties. After the as-deposited FePt thin films were annealed at various temperatures and furnace cooled, it is found that the ordering temperature of L1(0) FePt phase could be reduced to 350 degrees C. For FePt thin films annealed at 350 degrees C, the in-plane and out-of-plane coercivities of the films increased to 510 and 543 kA/m, respectively, and the films had hard magnetic properties. A highly (001) orientation was obtained, when FePt thin films were annealed at 600 degrees C. And the hysteresis loops of FePt thin films annealed at 600 degrees C show out-of-plane magnetic anisotropy. (C) 2009 Elsevier B.V. All rights reserved.