In this paper, we review our recent investigations on the magnetic properties and microstructure of highly coercive FePt films prepared on both MgO (001) and MgO (110) substrates with various film thicknesses (t N). Perpendicularly magnetized FePt (001) film were obtained on MgO (001) substrates, while FePt (101) films with the easy magnetization axis canted from the perpendicular direction to the film plane were obtained on MgO (110) substrates. The film morphology changes from a particulate to a continuous state depending on tN. A drastic decrease in the coercivity has been observed with the percolation of particles for FePt (001) films, when tN exceeds a critical thickness, TC = 45 nm. On the other hand, the gradual decrease of HC with tN has been observed in FePt (101) films and no remarkable change is seen at the critical thickness where the film morphology changes from a particulate to continuous state.
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