Structurally hidden magnetic transitions in Fe_3C at high pressures

摘要

We report a Mossbauer spectroscopic study of cementite (Fe_3C) in a diamond anvil cell up to 88 GPa. The hyperfine parameters reveal a two-stage loss of magnetism in Fe_3C: a ferro-to-paramagnetic transition around 8-10 GPa and a spin transition at about 22 GPa. Full structural refinement based on single-crystal x-ray diffraction data collected at pressures up to ~50 GPa reveals that there are no structural changes associated with the electronic transitions in Fe_3C. Our Rapid Communication resolves the long-standing controversy regarding the nature of phase transitions in Fe_3C at high pressures.