Granular L1 0 FePt (001) thin films were deposited on a Si substrate with Ta/MgO underlayers by rf sputtering. The effects of in-situ heating temperatures (350–575°C), pressures (2–40mTorr), and sputtering powers (15–75W) on texture and microstructure were investigated for the FePt films. We obtained films with grain densities approaching 50teragrains per in. 2 , grains sizes down to 2.2nm with center-to-center spacing of 4.2nm and coercivity of 24kOe. The order parameters for the L1 0 FePt thin films were derived and calculated to be as high as 0.91. Although the grain size is small, the spacing between grains is too large for practical heat assisted magnetic recording media. To reach the desired results, we propose that layer-by-layer growth should be promoted in the FePt layer by inserting another underlayer that provides a better lattice match to L1 0 FePt.