Fe3Si thin films were deposited on Si(001) from magnetron sputtering with varying deposition rates and subjected to post-deposition anneal (PDA). Structural investigations via XRD, SIMS and cross-sectional TEM reveal that high rate-deposited Fe3Si is amorphous while low rate-deposited Fe3Si is poly-crystalline with significant differences observed at the Fe3Si/Si interfaces. The structural differences were attributed to the influence of deposition rate on the grain nucleation and microstructural morphology in the as-deposited Fe3Si and the subsequent annealed films which in turn determine the ferromagnetic properties. Magnetic properties of Fe3Si deposited at high rate degrade with PDA - coercive field Hc increases from 1 to 14 Oe while saturation magnetization Ms decreases from ˜940 to 590 emu/cm3. In contrast, Fe3Si film sputter-deposited at low rate has a Hc of 5 Oe, Ms of ˜920 emu/cm3 and remnant magnetization Mr ˜0.9Ms that are maintained even upon PDA at 350 oC.