Preparation, Microstructure, and Magnetic Properties of Electrodeposited Nanocrystalline L10FePt Films

In this work, we prepared the nanocrystalline near-equiatomic FePt thin films by electrodeposition and explored the effects of annealing temperature and annealing time on morphology, structure, and magnetic properties of FePt film. The fcc-FePt phase starts to form when annealing at 400 degrees C under the 15% H(2)gas mixture. With increasing annealing temperature from 400 to 800 degrees C, the FePt film experiences a gradual phase transformation from the soft magnetic fcc phase to the permanent magnetic fct L1(0)phase. The transition degree of the L1(0)phase is achieved to be 0.94 and coercivity reaches a maximum of 1.5 T for the sample annealed at 800 degrees C for 4 h. A shoulder behavior in theM(H) curves is found in the electrodeposited FePt films. Through fitting theM(H) curves by the model based on the transition degree of the L1(0)FePt phase, the shoulder behavior is quantitatively confirmed to originate from the coexistence of the soft magnetic fcc phase and the permanent magnetic L1(0)phase. The magnetic exchange coupling between the soft magnetic and permanent magnetic nanocrystalline phases is negligible in the electrodeposited FePt films due to that the substrate Ag diffusion into the FePt film separates the FePt nanocrystalline phases.