Relating the magnetic coercivity to the L10 ordered FePd phase in annealed FexPd100-x nanoparticles

Abstract

Rare-earth-free or iron-based permanent nanomagnets are emerging as promising candidates for energy-conversion and information technologies. In this interest, FexPd100-x nanoparticles (x = 50, 55, 60, and 63) were prepared from iron acetate and palladium acetate by sonoelectrodeposition. After annealing the nanoparticles at various temperatures from 450 to 700 °C for 1 h, structural changes were observed, and the samples exhibit hard magnetic properties that depend strongly on chemical composition and annealing temperature. The major phase in the as-prepared nanoparticles has a disordered face-centered cubic structure, which, upon annealing, transforms into a multi-phase material containing a L10 ordered FePd phase. The fractions of different phases present in the annealed samples, including that of the L10 phase as functions of chemical composition and annealing temperature, are quantified by means of X-ray diffraction and scanning transmission electron microscopy. Magnetic measurements show the desirable hard magnetic properties for the samples annealed at 550–600 °C. A correlation between the magnetic coercivity and the L10 ordered FePd phase fraction is established for the first time in the FexPd100-x nanoparticles.