Local atomic and magnetic structures of nanocrystalline Fe75Cr10B15 alloy

Abstract

The crystal, local atomic and magnetic structures of Fe75Cr10B15 alloys annealed at 440–473°C for 5 min have been studied using X-ray diffraction and 57Fe Mossbauer spectroscopy. At the annealing temperature T a = 440°C, nanocrystals of the α-Fe phase (∼1%) precipitate in the amorphous matrix of the alloy. The complete crystallization of the amorphous alloy occurs at T a = 473°C with the formation of α-Fe nanocrystals 26 ± 2 nm in size and nanocrystals of tetragonal boride t-Fe3B 47 ± 2 nm in size. It has been found that chromium atoms are located in nanocrystals of the α-Fe and y-Fe3B types. The distribution functions of hyperfine fields in the nanocrystalline Fe75Cr10B15 alloy reconstructed from the Mossbauer spectra (at T a = 473°C) show that there are three allowed states of iron atoms in the α-Fe phase and three equally probable crystallographic nonequivalent states of iron in the t-(Fe,Cr)3B phase. The chromium concentration x in the α-Fe(Cr) phase is found to be ∼10 at %. The substitution of chromium atoms for iron atoms in t-Fe3B substantially decreases local magnetic moments of the iron atoms.