Order-Disorder Transformation in Fe₅₀Co₅₀ Particles Synthesized by Polyol Process

Abstract

X-ray diffraction applied anomalous dispersion effect was used for characterizing the order-disorder transformation in Fe₅₀Co₅₀ fine particles synthesized by polyol process. The long range order parameter was estimated from the superlattice peak intensities in the diffraction pattern of particles annealed in the temperature range between 20 and 800°C. The results showed that fine particles of as-synthesized Fe-Co have a disordered structure at room temperature, while the ordered structure is present, to a great extent, in Fe-Co bulk alloys. The fine particles of the disordered alloy were transformed to the ordered state by annealing up to about 450°C. The magnetic properties of the Fe-Co alloy fine particles annealed at different temperatures were also investigated using a vibrating sample magnetometer, in which magnetic fields of up to 15 kOe were applied to samples at room temperature. The saturation magnetization of the as-synthesized particles increased with annealing temperature. This may be attributed to transformation from disordered to ordered structure, along with sintering.