Reinterpretation of Report of Tetrataenite in Bulk Alloy Castings.

After the publication of "Direct formation of hard-magnetic tetrataenite in bulk alloy castings" Ivanov et al., Advanced Science 10 (2022) 2204315, the authors identified a potential misinterpretation of the experimental data. Further work confirms that the original conclusions cannot be supported, and accordingly the paper is retracted. X-ray diffraction shows the presence of (Fe,Ni)P, giving additional Bragg peaks that were previously attributed to tetrataenite. Extra Bragg reflections observed in transmission electron diffraction, and earlier considered to be superlattice reflections from tetrataenite, instead result from oxidation of the sample surface during preparation. Measurements of magnetic hysteresis show no regions of high coercivity of the kind expected when tetrataenite is present. It is concluded that as-cast bulk samples of Fe-Ni-P-(C) show no evidence of tetrataenite on any length scale. Nevertheless, the addition of phosphorus should remain of interest in ongoing efforts to manufacture tetrataenite.