Evidence of Dipolar Magnetic Interaction in Melted Fe₅₀Al₅₀ Samples

Powders of the Fe₅₀Al₅₀ melted and heat treated samples were separated at different mean particle sizes as well as characterized based on their structural and magnetic properties. All the samples, except that with biggest particle size, showed Fe-Al BCC and α-Fe phases as well as the same nanostructure. The powder with the biggest particles, with particle size bigger than 105 μm, presents the additional minority presence of FeO and Al₂O phases. The powders were found to be ferromagnetic at room temperature with a mean hyperfine magnetic field (MHMF) that increases with increasing particle size. The origin of the increase of the MHMF is attributed to the increment of the magnetic dipolar interactions between the magnetic moment of each particle and the field produced by other magnetic moments of their surrounded particles. This field also increases as the particle size increases. Besides the dipolar magnetic interaction between particles, the Fe-Al and α-Fe grains present a ferromagnetic coupling between them.