Structure and Magnetic Properties of Nanocrystalline Fe55Pd45 Processed by Sonoelectrodeposition

Fe 55 Pd 45 nanoparticles were prepared from iron acetate and palladium acetate by sonoelectrodeposition. The as-prepared nanoparticles were annealed at various temperatures from 450°C to 700°C for 1 h in order to study the effect of heat treatment on the phase composition, particle size and magnetic properties. The phase composition and the crystallite size of the annealed samples were determined by x-ray diffraction while the particle size was studied by transmission electron microscopy. It was revealed that the magnetic properties of the samples depend on the phase composition of the material. The as-prepared nanoparticles had a disordered face-centered cubic (fcc) structure which transformed to a multi-phase material containing an ordered L1 0 FePd phase and a body-centered cubic Fe after annealing at 550°C; however, a disordered fcc FePd also remained in the material. The ordering in the structure yielded a significant increase in the room-temperature coercivity from 0.5 kOe to 1.1 kOe. At 700°C, the coercivity decreased due to the formation of a disordered fcc γ-FePd phase. In addition to the phase transformation, the average crystallite size grew from about 8 nm to 50–70 nm during annealing.