The influence of annealing temperature on hyperfine magnetic field and saturation magnetization of Fe–Si–Al–Cr flake-shaped particles

Abstract

Fe75Si13Al10Cr2 flake-shaped particles were prepared from crushing ingots with ball milling method. In order to explore the relationship between microstructure and saturation magnetization (Ms), the particles were annealed under nitrogen atmosphere at different temperature. The XRD results show that the DO3 ordered phase coexists with α-Fe (Si, Al, Cr) matrix phase by annealing above 500 °C. Mössbauer spectroscopy measurements show that the hyperfine magnetic field (HMF) of the original particles has wide distribution. On the contrary, the HMF of the annealed powders can be easily distinguishable with each other, indicating that the crystal structure of the material has a disorder-order change. The Mössbauer spectra can be fitted with 4 sextets representing 4 different Fe-site environments, and there is a significant change on the ratios of Fe-site environments with annealing temperature. The change leads to an obviously increase of the average hyperfine magnetic field (<HMF>) with increasing annealing temperature. For this alloy, Ms has linear relationship with Fe atomic magnetic moment (μFe) and <HMF> has an approximate linear relationship with μFe. So the Ms of the particles also has an obviously increase with annealing temperature. Ms and <HMF> have an obvious turning point at 600 °C, because of the HMF values decrease of 8Fe-site and 6Fe-site, which comes from a DO3-B2 ordered transformation.