Magnetic Properties and Microstructure of Fe/FePt Films with Perpendicular Magnetization

The soft/hard Fe/FePt bilayer with perpendicular magnetization has been prepared successfully on glass substrate. The (001) oriented L1(0) FePt film with fix thickness 10nm was deposited on glass and subsequently annealing by rapid thermal process (RTP) at 800 degrees C for 5 minutes and a Fe layer was deposited at room temperature with thickness of 2nm to 10nm. The control of Fe layer thickness allowed modifying the hysteresis loops from rigid magnet to exchange-spring magnet due to the nanoscale soft/hard interface coupling. When the Fe layer thickness increased to 3nm, the out-of-plane coercivity is reduced to 5.88 kOe but the remanence ratio (0.98) is high. The Fe (3nm)/FePt bilayer shows perpendicular magnetization with linear in-plane hysteresis loop. The remanence ratio is reduced to 0.86 when the Fe layer thickness increased up to 6nm. When the Fe layer increased up to 10nm, the hysteresis loop shows exchange spring-like behavior. The out-of-plane coercivity is still 4kOe but the remanence ratio is 0.19. The films with perpendicular coercivity were moderated successfully by the soft magnetic layer with different thickness.