Understanding the enhanced microwave permeability of Fe–Si–Al particles by Mössbauer spectroscopy

The microwave permeability of milled Fe–Si–Al flaky particles has been found to be much larger than those of unmilled particles with irregular shape. Transmission Mössbauer spectra are found significantly different for particles with different shapes. More than 8 absorption peaks have been found for the unmilled particles while there are only 6 absorption peaks for the flaky particles. The unmilled particles are found with the ordered D03 type superlattice structure. Therefore the Mössbauer spectra can be fitted with 5 sextets representing 5 different Fe-site environments. However, the flaky particles are with the disorder α-Fe(Si,Al) structure, and their Mössbauer spectra can be fitted with a model with the distribution of hyperfine magnetic field and isomer shift. It also has been revealed by Mössbauer spectroscopy that the flaky particles have stronger tendency to possess the planar magnetic anisotropy, and their average magnetic moment is found to be about 1.63μB.

► Microwave permeability of FeSiAl particles can be greatly enhanced in flaky particles.
► Mössbauer spectra show the changes of crystal structure due to the ball milling.
► Mössbauer measurements show that flaky particles have a stronger planar anisotropy.