57Fe Mossbauer study of hexagonal phase iron alloys

Abstract

The authors study the HCP ( epsilon phase) alloys of Fe with Ru and Os, containing 15 and 30 at.% of the alloying element, using ⁵⁷Fe Mossbauer absorption spectroscopy. The existence of antiferromagnetism in the Fe-Ru and probably the Fe_0.85 Os_0.15 alloys was indicated. The saturated hyperfine fields and Neel temperatures for the 15 and 30 at. Ru and 15 at.% Os alloys were 15 kG and 210K, 13 kG and 60K, 3.3 kG and 30K, respectively, orientated at 50+or-10 degrees to the nuclear EFG; the latter showed a slight negative temperature gradient and was deduced to be probably negative in sign. The alloy Fe_0.7 Os_0.3 showed no sign of magnetism, at any temperature. The magnitude of the EFGs was consistent with the quantity and size of the solute atoms, and extrapolated to the experimentally observed value for pure HCP Fe. Extrapolations of the hyperfine fields and Neel temperatures to pure epsilon -Fe yielded 17 kG and 360K, respectively, consistent with a theoretical, physically unrealisable, 'negative pressure' HCP phase.