Accelerating Nature: Induced Atomic Order in Equiatomic FeNi

The production of locally atomically ordered FeNi (known by its meteoric mineral name, tetrataenite) is confirmed in bulk samples by simultaneous conversion X-ray and backscattered gamma-ray 57Fe Mossbauer spectroscopy. Up to 22 volume percent of the tetragonal tetrataenite phase is quantified in samples thermally treated under simultaneous magnetic- and stress-field conditions for a period of 6 weeks, with the remainder identified as the cubic FeNi alloy. In contrast, all precursor samples consist only of the cubic FeNi alloy. Data from the processed alloys are validated using Mossbauer parameters derived from natural meteoritic tetrataenite. The meteoritic tetrataenite exhibits a substantially higher degree of atomic order than do the processed samples, consistent with their low uniaxial magnetocrystalline anisotropy energy of approximate to 1 kJ center dot m-3. These results suggest that targeted refinements to the processing conditions of FeNi will foster greater atomic order and increased magnetocrystalline anisotropy, leading to an enhanced magnetic energy product. These outcomes also suggest that deductions concerning paleomagnetic conditions of the solar system, as derived from meteoritic data, may warrant re-examination and re-evaluation. Additionally, this work strengthens the argument that tetrataenite may indeed become a member of the advanced permanent magnet portfolio, helping to meet rapidly escalating green energy imperatives. Processing-induced atomic order is confirmed in FeNi alloys and compared to that of its meteoritic analog, tetrataenite, using simultaneous conversion X-ray and backscattered gamma-ray 57Fe Mossbauer spectroscopy. The concurrent application of saturating magnetic field and strain applied during 6 weeks of thermal treatment creates up to 22 vol.% of the ordered phase, of interest for future advanced permanent magnets.image