A study led by Dr. Aoki, investigating the magnetic transition of iron using neutron diffraction, has been published in Physical Review B.
The crystal structure of iron changes with temperature and pressure, and magnetism plays an important role in its phase stability. However, the relationship between magnetic and structural transitions under high pressure has not been well understood. In this study, we investigated the temperature dependence of magnetization in α-iron by directly observing magnetic scattering from iron in in situ neutron diffraction experiments. Our results show that the Curie temperature, at which iron loses its ferromagnetism, decreases significantly with pressure, from 1043 K at ambient pressure to 740 K at 6.7 GPa. Furthermore, at 6.7 GPa, the structural transition from the α phase to the γ phase occurs after this magnetic transition. This demonstrates that the α–γ transition is a transformation from a paramagnetic body-centered cubic structure to a paramagnetic face-centered cubic structure.
Aoki K., Takano M., Fukuyama K., Kagi H., Machida A., Smith H., Hattori T., Sano-Furukawa A., and Funakoshi K. (2026) Spontaneous magnetization curve of α-iron at high pressures determined using in situ neutron diffraction. Phys. Rev. B 113, 184440.